Austin Community College Rene Descartess Skeptical Argument Discussion Board

Q1. 300-500 words. What is ReneDescartes’s skeptical argument against taking perception asjustification? Is his argument sound? Why or why not? What might acritic say to you in response?

Then, state whether you think his argument is sound, and offeryour critical argument for thinking so. Is the argument valid? Are allof its premises true? Explain.Finally, consider how Descartes’s might respond to yourassessment. If you think his argument is unsound, then state a potentialreply on his behalf. If you think the argument is sound, state apotential reply on behalf of the dogmatist and defend Descartes’sposition

Knowledge1
by Simon Blackburn, 1999
English Analytic Philosopher
Perhaps the most unsettling thought many of us have, often quite early on in
childhood, is that the whole world might be a dream; that the ordinary scenes
and objects of everyday life might be fantasies. The reality we live in maybe a
virtual reality, spun out of our own minds, or perhaps injected into our minds
by some sinister Other. Of course, such thoughts come, and then go. Most of
us shake them off. But why are we right to do so? How can we know that the
world as we take it to be, is the world as it is?
How do we begin to think about the relation between appearance and
reality: things as we take them to be, as opposed to things as they are?
Losing the World
We might say: it all began on 10 November 1619.
On that date, in the southern German town of Ulm, the French
mathematician and philosopher René Descartes (1596-1650) shut himself away
in a room heated by a stove, and had a vision followed by dreams, which he
took to show him his life’s work: the unfolding of the one true way to find
knowledge. The true path required sweeping away all that he had previously
taken for granted, and starting from the foundations upwards.
Of course, it didn’t, really, begin in 1619, for Descartes was not the first.
The problems Descartes raised for himself are as old as human thought. These
are problems of the self, and its mortality, its knowledge, and the nature of the
world it inhabits; problems of reality and illusion. They are all raised in the oldest
1
From Blackburn’s 1999 Think: A Compelling Introduction to Philosophy, chapter 1. Oxford UP.
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philosophical texts we have, the Indian Vedas, stemming from about 1500 B.C.
The generation immediately before Descartes had included the great French
essayist Montaigne, whose motto was the title of one of his great essays: “Que
sais-je?” — what do I know?
Nor did Descartes come to his enterprise with a totally innocent mind:
he himself had an intense education in the prevailing philosophies of the time,
at the hands of Jesuit teachers. But by Descartes’s time things were changing.
The Polish astronomer Copernicus had discovered the heliocentric (suncentred) model of the solar system. Galileo and others were laying the
foundations of a “mechanical” science of nature. In this picture the only
substances in space would be material, made up of “atoms”, and caused to
move only by mechanical forces which science would eventually discover. Both
Copernicus and Galileo fell foul of the guardians of Catholic orthodoxy, the
Inquisition, for this scientific picture seemed to many people to threaten the
place of human beings in the cosmos. If science tells us all that there is, what
becomes of the human soul, human freedom, and our relationship with God?
Descartes was smart. He invented standard algebraic notation; and
Cartesian coordinates, which enable us to give algebraic equations for
geometrical figures, are named after him. He himself was one of the leaders of
the scientific revolution, making fundamental advances not only in
mathematics but also in physics, particularly optics. But Descartes was also a
pious Catholic. So for him it was a task of great importance to show how the
unfolding scientific world — vast, cold, inhuman, and mechanical — nevertheless
had room in it for God and freedom, and for the human spirit.
Hence his life’s work, culminating in the Meditations, published in 1641,
“in which are demonstrated the existence of God and the distinction between
the human soul and the body”, according to the subtitle. But the subtext is that
Descartes also intends to rescue the modern world view from the charge of
atheism and materialism. The scientific world is to be less threatening than was
feared. It is to be made safe for human beings. And the way to make it safe is
to reflect on the foundations of knowledge. So we start with Descartes because
he was the first great philosopher to wrestle with the implications of the
modern scientific world view. Starting with the medievals or Greeks is often
starting so far away from where we are now that the imaginative effort to think
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in their shoes is probably too great. Descartes is, comparatively, one of us, or
so we may hope.
There is a danger in paraphrasing a philosopher, particularly one as terse
as Descartes. I am going to present some of the central themes of the
Meditations. This is in the spirit of a sportscast showing only the “edited
highlights” of a game. Closer acquaintance with the text would uncover other
highlights; closer acquaintance with its historical context would uncover yet
others. But the highlights will be enough to illuminate most of the central issues
of subsequent philosophy.
The Evil Demon
There are six Meditations. In the first, Descartes introduces the “method of
doubt”. He resolves that if he is to establish anything in the sciences that is
“stable and likely to last” he must demolish all his ordinary opinions, and start
right from the foundations.
For he has found that even his senses deceive him, and it is “prudent
never to trust completely those who have deceived us even once”. He puts to
himself the objection that only madmen (“who say that they are dressed in
purple when they are naked, or that their heads are made of earthenware, or
that they are pumpkins or made of glass” — madmen were evidently pretty
colourful in the seventeenth century) deny the very obvious evidence of their
senses.
In answer to that, he reminds us of dreams, in which we can represent
things to ourselves just as convincingly as our senses now do, but which bear
no relation to reality.
Still, he objects to himself, dreams are like paintings. A painter can
rearrange scenes, but ultimately depicts things derived from “real” things, if
only real colours. By similar reasoning, says Descartes, even if familiar things
(our eyes, head, hands, and so on) are imaginary, they must depend on some
simpler and more universal things that are real.
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But what things? Descartes thinks that “there is not one of my former
beliefs about which a doubt may not properly be raised”. And at this stage,
I will suppose therefore that not God, who is supremely good and the source of
truth, but rather some malicious demon of the utmost power and cunning has
employed all his energies in order to deceive me. I shall think that the sky, the
air, the earth, colours, shapes, sounds and all external things are merely the
delusions of dreams which he has devised to ensnare my judgment.
This is the Evil Demon. Once this frightening possibility is raised, his only
defence is resolutely to guard himself against believing any falsehoods. He
recognizes that this is hard to do, and “a kind of laziness” brings him back to
normal life, but intellectually, his only course is to labour in the “inextricable
darkness” of the problems he has raised. This ends the first Meditation.
Cogito, Ergo Sum
The second Meditation begins with Descartes overwhelmed by these doubts.
For the sake of the inquiry he is supposing that “I have no senses and no body”.
But:
Does it now follow that I too do not exist? No: if I convinced myself of
something then I certainly existed. But there is a deceiver of supreme power
and cunning who is deliberately and constantly deceiving me. In that case I too
undoubtedly exist, if he is deceiving me; and let him deceive me as much as he
can, he will never bring it about that I am nothing so long as I think that I am
something. So after considering everything very thoroughly, I must finally
conclude that this proposition, I am, I exist, is necessarily true whenever it is put
forward by me or conceived in my mind.
This is the famous “Cogito, ergo sum”: “I think, therefore I am.”
Having saved his “self” out of the general seas of scepticism, Descartes
now asks what this self is. Whereas formerly, he thought he knew what his body
was, and thought of himself by way of his body, now he is forced to recognize
that his knowledge of his self is not based on knowledge of his embodied
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existence. In particular, he is going to meet problems when he tries to imagine
it. Imagination is a matter of contemplating the shape or image of a corporeal
thing (a body, or thing extended in space). But at this stage, we know nothing
of corporeal things. So “imagining” the self by imagining a thin or tubby, tall or
short, weighty bodily being, such as I see in a mirror, is inadequate.
So what is the basis of this knowledge of the self?
Thinking? At last I have discovered it — thought; this alone is inseparable
from me. I am, I exist — that is certain. But for how long? For as long as I am
thinking. For it could be, that were I totally to cease from thinking, I should
totally cease to exist. . . I am, then, in the strict sense only a thing that thinks.
The inquiry now takes a slightly different course. Descartes recognizes
that a conception of oneself as an embodied thing, living in an extended spatial
world of physical objects, will come back almost irresistibly. And he realizes that
the “I” he is left with is pretty thin: “this puzzling I that cannot be pictured in
the imagination”. So “let us consider the things which people commonly think
they understand most distinctly of all; that is the bodies we touch and see”. He
considers a ball of wax. It has taste and scent, and a colour, shape, and size
“that are plain to see”. If you rap it, it makes a sound. But now he puts the wax
by the fire, and look:
[“I”]he residual taste is eliminated, the smell goes away, the colour
changes, the shape is lost, the size increases; it becomes liquid and hot;
you can hardly touch it, and if you strike it, it no longer makes a sound. But
does the same wax remain? It must be admitted that it does; no one denies
it, no one thinks otherwise. So what was it in the wax that I understood
with such distinctness? Evidently none of the features which I arrived at by
means of the senses; for whatever came under taste, smell, sight, touch or
hearing has now altered — yet the wax remains.
Descartes glosses the result of this example as showing that there is a
perception of the wax that is “pure mental scrutiny”, which can become “clear
and distinct” depending on how careful he is to concentrate on what the wax
consists in. So, by the end of the second Meditation, he concludes:
I now know that even bodies are not strictly perceived by the senses or
the faculty of imagination but by the intellect alone, and that this perception
derives not from their being touched or seen but from their being understood;
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and in view of this I know plainly that I can achieve an easier and more evident
perception of my own mind than of any thing else.
Motivations, Questions
How are we to read a piece of philosophy like this? We start by seeing Descartes
trying to motivate his method of extreme doubt (also known as Cartesian
doubt, or as he himself calls it, “hyperbolic”, that is, excessive or exaggerated
doubt). But is the motiva-tion satisfactory? What exactly is he thinking? Perhaps
this:
The senses sometimes deceive us. So for all we know, they always
deceive us.
But that is a bad argument — a fallacy. Compare:
Newspapers sometimes make mistakes. So for all we know, they always
make mistakes.
The starting point or premise is true, but the conclusion seems very
unlikely indeed. And there are even examples of the argument form where the
premise is true, but the conclusion cannot be true:
Some banknotes are forgeries. So for all we know, they all are forgeries.
Here, the conclusion is impossible, since the very notion of a forgery
presupposes valid notes or coins. Forgeries are parasitic upon the real. Forgers
need genuine notes and coins to copy.
An argument is valid when there is no way — meaning no possible way -that the premises, or starting points, could be true without the conclusion
being true (we explore this further in Chapter 6). It is sound if it is valid and it
has true premises, in which case its conclusion is true as well. The argument just
identified is clearly invalid, since it is no better than other examples that lead us
from truth to falsity. But this in turn suggests that it is uncharitable to interpret
Descartes as giving us such a sad offering. We might in-terpret him as having in
mind something else, that he regrettably does not make explicit. This is called
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looking for a suppressed premise — something needed to buttress an argument,
and that its author might have presupposed, but does not state. Alternatively
we might reinterpret Descartes to be aiming at a weaker conclusion. Or
perhaps we can do both. The argument might be:
The senses sometimes deceive us. We cannot distinguish occasions
when they do from ones when they do not. So for all we know, any particular
sense experience may be deceiving us.
This seems to be a better candidate for validity. If we try it with
banknotes and forgeries, we will find that the conclusion seems to follow. But
the conclusion is a conclusion about any particular experience. It is no longer
the conclusion that all our experience (en bloc, as it were) may be deceiving us.
It is the difference between “for all we know any particular note may be a
forgery” and “for all we know all notes are forgeries”. The first may be true
when the second is not true.
Still, perhaps at this stage of the Meditations the weaker conclusion is
all Descartes wants. But we might also turn attention to the second premise of
this refined argument. Is this premise true? Is it true that we cannot distinguish
occasions of error — things like il-lusions, delusions, misinterpretations of what
we are seeing — from others? To think about this we would want to introduce a
distinction. It may be true that we cannot detect occasions of illusion and error
at a glance. That is what makes them illusions. But is it true that we cannot do
so given time? On the contrary, it seems to be true that we can do so: we can
learn, for instance, to mistrust images of shimmering water in the desert as
typically misleading illusions or mirages — tricks of the light. But worse, the fact
that we can detect occasions of deception is surely presupposed by Descartes’s
own argument. Why so? Because Descartes is presenting the first premise as a
place to start from — a known truth. But we only know that the senses
sometimes deceive us because further investigations — using the very same
senses — show that they have done so. We find out, for instance, that a quick
glimpse of shimmering water misled us into thinking there was water there. But
we discover the mistake by going closer, looking harder, and if neces-sary
touching and feeling, or listening. Similarly, we only know, for instance, that a
quick, off-the-cuff opinion about the size of the Sun would be wrong because
further laborious observations show us that the Sun is in fact many times the
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size of the Earth. So the second premise only seems true in the sense of “we
cannot distinguish at a glance whether our senses are deceiving us”. Whereas
to open the way to Descartes’s major doubts, it would seem that he needs “we
cannot distinguish even over time and with care whether our senses are
deceiving us”. And this last does not seem to be true. We might try saying that
the senses are “self-corrective”: further sense experience itself tells us when a
particular sense experience has induced us to make a mistake.
Perhaps anticipating this kind of criticism, Descartes introduces the
topic of dreams. “Inside” a dream we have experiences which bear some
resemblance to those of ordinary living, yet nothing real corresponds to the
dream. Is Descartes’s idea here that the whole of experience may be a dream?
If so, once again we might use a distinction like the one we just made: perhaps
we cannot distinguish immediately or “at a glance” whether we are dreaming,
but using our memory, we seem to have no trouble distinguishing past dreams
from past encounters with reality.
Still, there is something troubling about the idea that all experience
might be a dream. For how could we set about determining whether that is
true? Sometimes people “pinch themselves” to ensure that they are not
dreaming. But is this really a good test? Might we not just dream that the pinch
hurts? We might try from within a dream to discover whether it is a dream. Yet
even if we think up some cunning experiment to determine whether it is, might
we not just dream that we conduct it, or dream that it tells us the answer that
we are awake?
We might try saying that events in everyday life exhibit a scale and a
sheer coherence that dreams do not exhibit. Dreams are jerky and spasmodic.
They have little or no rhyme or reason. Experience, on the other hand, is large
and spacious and majestic. It goes on in regular ways — or at least we think it
does. However, it is then open for Descartes to worry whether the scale and
coherence is itself deceptive. That takes him to the Evil Demon, one of the most
famous thought-experiments in the history of philosophy. It is a thoughtexperiment designed to alert us to the idea that, so far as truth goes, all our
experience might be just like a dream: totally disconnected from the world.
It is important to seize on two things at the outset. First, Descartes is
perfectly well aware that as active, living, human agents we do not bother
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ourselves about such an outlandish possibility. In fact, we cannot: as many
philosophers have pointed out, it is psychologically impossible to keep doubt
about the external world alive outside the study. But that does not matter. The
doubt is worth bothering about because of the task he is engaged upon. This is
the task of finding foundations of knowledge, of ensuring that his beliefs are
built on a sound footing. Descartes’s inquiry is made for purely intellectual
reasons. Second, Descartes is not asking you to believe in the possibility of the
Evil Demon. He is only asking you to consider it — en route to getting clear how
to dismiss it. That is, he thinks (not unreasonably, surely?) that unless this
possibility can be dismissed, there remains a challenge of scepticism: the
possibility that we have no knowledge, but that all our beliefs are entirely
delusive.
We can appreciate the thought-experiment by reminding ourselves how
very “realistic” a virtual reality can become. Here is an updated variant of the
thought-experiment. Imagine an advance in science that enables a mad
scientist to extract your brain, and then to maintain it in a vat of chemicals that
sustain its normal functioning. Imagine that the scientist can deliver inputs to
the normal information channels (the optic nerve, the nerves that transmit
sensations of hearing and touch and taste). Being good-natured, the scientist
gives information as if the brain were lodged in a normal body and living a
reasonable life: eating, playing golf, or watching TV. There would be feedback,
so that for instance if you deliver an “output” equivalent to raising your hand,
you get “feedback” as if your hand had risen. The scientist has put you into a
virtual reality, so your virtual hand rises. And, it seems, you would have no way
of knowing that this had happened, since to you it would seem just as if a
normal life was continuing.
Descartes’s own version of the thought-experiment does not cite brains
and vats. In fact, if you think about it, you will see that he does not need to do
so. Our beliefs about the brain and its role in generating conscious experience
are beliefs about the way the world works. So perhaps they too are the result
of the Evil Demon’s inputtings! Perhaps the Demon did not need to get his
hands (?) dirty messing around in vats. He just inputs experiences in whatever
way is made appropriate by the real reality. Brains and nerves themselves
belong to the virtual reality.
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This thought-experiment does not cite actual illusions of sense, or actual
dreams. It simply sets experience as a whole against a very different and
potentially disturbing reality. Notice as well that it is not obviously useful to
argue against the Evil Demon hypothesis by citing the coherence and scale of
everyday experience. For we do not know of any reason why the Demon could
not input experience as coherent as he wishes, and of whatever scale or extent
he wishes.
So how could we possibly rule out the Evil Demon hypothesis? Once it is
raised, we seem to be powerless against it.
Yet, in this sea of doubt, just when things are at their darkest, Descartes
finds one certain rock upon which he can perch. “Cogito, ergo sum”: I think,
therefore I am. (A better translation is “I am thinking, therefore I am”.
Descartes’s premise is not “I think” in the sense of “I ski”, which can be true
even if you are not at the moment skiing. It is supposed to be parallel to “I am
skiing”.)
Even if it is a virtual reality that I experience, still, it is I who experience
it! And, apparently I know that it is I who have these experiences or thoughts
(for Descartes, “thinking” includes “experiencing”).
Why does this certainty remain? Look at it from the Demon’s point of
view. His project was to deceive me about everything. But it is not logically
possible for him to deceive me into thinking that I exist when I do not. The
Demon cannot simultaneously make both these things true:
I think that I exist.
I am wrong about whether I do.
Because if the first is true, then I exist to do the thinking. Therefore, I
must be right about whether I exist. So long as I think that (or even think that I
think it), then I exist.
I can think that I am skiing when I am not, for I may be dreaming, or
deluded by the Demon. However, I cannot think that I am thinking when I am
not. For in this case (and only this case) the mere fact that I think that I am
thinking guarantees that I am thinking. It is itself an example of thinking.
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The Elusive “I”
Outside the context of the doubt, the “I” that thinks is a person that can be
described in various ways. In my case, I am a middle-aged professor of
philosophy, with a certain personality, a history, a network of social relations, a
family, and so on. But in the context of the doubt, all this is swept away: part of
the virtual reality. So what is the “I” that is left? It seems very shadowy — a pure
subject of thought. It might not even have a body! This takes us to the next
twist.
You might try peering into your own mind, as it were, to catch the
essential “you”. But, remembering that the “you” (or the “I”, from your point
of view) is here separated from normal marks of identity (your position in
space, your body, your social relations, your history), it seems there is nothing
to catch. You can become aware of your own experiences, but never, it seems,
aware of the “I” that is the subject of those experiences. Or you can try to
imagine the self, to frame a picture of it, as it were. But as Descartes remarks,
imagination seems good at framing pictures of things that have shape and size,
and are found in space (“extended things”). The self that remains as the rock in
the seas of doubt may not be an extended thing. For we can be certain of it
when we are still uncertain about extended things, since we are taking seriously
the possibility of the Evil Demon.
One reconstruction of this point of the argument presents Descartes
thinking like this:
I cannot doubt that I exist. I can doubt whether things extended in space
(“bodies”) exist. Therefore, I am not a body.
In a nutshell, souls are certain, bodies are doubtful, so the soul is distinct
from the body. If this is Descartes’s argument, then it is superficially plausible,
but can be seen to be invalid. For consider the parallel:
I cannot doubt that I am here in the room. I can doubt whether a person
who will get bad news tomorrow is in the room. Therefore, I am not a person
who will get bad news tomorrow.
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A nice proof with a welcome result! The fallacy is often called the
“masked man fallacy”: I know who my father is; I do not know who the masked
man is; so, my father is not the masked man.
I myself doubt if Descartes committed this fallacy, at least in this
Meditation. At this point he is more concerned with the way in which we know
anything about souls and bodies. He is not concerned to prove that they are
distinct, but more concerned to show that knowledge of the self is not
dependent upon knowledge of bodies. Because the one can be certain, even
when the other is not. Nevertheless, what are we left really knowing about the
self?
In the following century the German philosopher Georg Christoph
Lichtenberg (1742-99) remarked: “We should say, ‘it thinks’ just as we say, ‘it
thunders’. Even to say ‘cogito’ is too much, if we translate it with ‘I think’.”
(Lichtenberg liked pithy aphorisms, and was an important influence on a yet
later figure, Friedrich Nietzsche [1844-1900].)
The idea is that the apparent reference to an “I” as a “thing” or subject
of thought is itself an illusion. There is no “it” that thunders: we could say
instead just that thunder is going on. Similarly Lichtenberg is suggesting, at
least in the context of the doubt, that Descartes is not entitled to an “I” that is
thinking. All he can properly claim is that “there is a thought going on”.
This seems a very bizarre claim. For surely there cannot be a thought
without someone thinking it? You cannot have thoughts floating round a room
waiting, as it were, for someone to catch them, any more than you can have
dents floating around waiting to latch onto a surface to be dented. We return
to this in Chapter 4. But then why isn’t Lichtenberg right? If Descartes cannot
confront a self that is doing the thinking, cannot experience it, cannot imagine
it, then why is he entitled to any kind of certainty that it exists? Indeed, what
can it mean to say that it exists?
Descartes adroitly puts this problem to one side, by raising a parallel
difficulty about “things which people commonly think they understand most
distinctly of all” — ordinary bodies, or things met with in space. This is what was
aimed at by the ball of wax ex-ample. Here is a possible reconstruction of the
argument:
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At a particular time, my senses inform me of a shape, colour, hardness,
taste that belong to the wax. But at another time my senses inform me of a
different shape etc. belonging to the wax. My senses show me nothing but
these diverse qualities (which we can call “sensory qualities”, since our senses
take them in). I nevertheless make a judgement of identity: it is the same piece
of wax on the earlier and the later occasion. So, it is the nature of the ball of
wax that it can possess different sensory qualities at different times. So, to
understand what the wax is I must use my understanding, not my senses.
If this is a good reconstruction, we should notice that Descartes is not
denying that it is by means of the senses that I know that the wax is there in
the first place (assuming we have got rid of the Evil Demon, and are back to
trusting our senses). In fact, he goes on to say as much. Rather, he is suggesting
that the senses are like messengers that deliver information that needs
interpreting. And this interpretation, which is here a question of identifying the
one object amongst the many successive appearances, is the work of the
understanding. It is a matter of employing principles of classification, or
categories, whose credentials we can also investigate.
So, all we can understand by the wax is that it is some elusive “thing”
that can take on different bodily properties, such as shape, size, colour, taste.
And we understand by the self, the “I”, just some equally elusive “thing” that
at different times thinks different thoughts. So maybe the self should not be
regarded as especially mysterious, compared with everyday things like the ball
of wax. Perhaps selves are no harder to understand than bodies, and we only
think otherwise because of some kind of prejudice. We return to the wax in
Chapter 7.
Clear and Distinct Ideas
The first two Meditations deserve their place as classics of philosophy. They
combine depth, imagination, and rigour, to an extent that has very seldom been
paralleled. So one is left with bated breath, waiting for the story to unfold. Here
is Descartes left perching on his one minute rock, surrounded by a sea of doubt.
But it seems he has denied himself any way of getting off it. Life may still be a
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dream. To use the metaphor of foundations: he is down to bedrock, but has no
building materials. For the very standards he set himself, of “demon-proof”
knowledge, seem to forbid him even from using “self-evident” or natural means
of reasoning, in order to argue that he knows more than the Cogito. There is
nothing difficult about the Demon deceiving us into listening to delusive pieces
of reasoning. Our reasonings are apt to be even more fallible than our senses.
Curiously, he does not see it quite like that. What he does is to reflect on
the Cogito, and ask what makes it so especially certain. He convinces himself
that it is because he has an especially transparent “clear and distinct”
perception of its truth. It is generally agreed that Descartes, the mathematician,
had a mathematical model of clarity in mind. Suppose, for instance, you think
about a circle. Imagine a diameter, and draw chords from the opposite ends to
a point on the circumference. They meet at a right angle. Draw others, and they
always seem to do so. At this point, you might have a not very clear sense that
perhaps there is a reason for this. But now, suppose you go through a proof
(drawing the line from the centre of the circle to the apex of the triangle, and
solving the two triangles you create). After that you can just see that the
theorem has to hold. This may come as a “flash”: a blinding certainty, or insight
into this particular piece of geometrical truth. This is just a random geometrical
example of a procedure that can make you “see” something that you might
only dimly have grasped. But if only we could see the rest of reality, mind, body,
God, freedom, human life, with the same rush of clarity and understanding!
Well, one philosophical ideal is that we can. This is the ideal of rationalism: the
power of pure unaided reason. For the rationalist can see from her armchair
that things must be one way and cannot be other ways, like the angle in the
semicircle. Knowledge achieved by this kind of rational insight is known as “a
priori”: it can be seen to be true immediately, without any experience of the
way of the world.
The Trademark Argument
Trusting clarity and distinctness, Descartes indulges a piece of reasoning.
Looking into his own “self”, which is all that he has at this point, Descartes
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discovers that he has an idea of perfection. He then argues that such an idea
implies a cause. However, the thing that caused it must have as much “reality”,
and that includes perfection, as the idea itself. This implies that only a perfect
cause, that is, God, will do. Hence God exists, and has left the idea of perfection
as an innate sign of his workmanship in our minds, like a craftsman leaving a
trademark stamped in his work.
Once Descartes has discovered God, the seas of doubt subside in a rush.
For since God is perfect, he is no deceiver: deceiving is clearly falling short of
goodness, let alone perfection. Hence, if we do our stuff properly, we can be
sure that we will not be the victims of illusion. The world will be as we
understand it to be. Doing our stuff properly mainly means trusting only clear
and distinct ideas. What are we to make of the “trademark” argument? Here is
a reconstruction:
I have the idea of a perfect being. This idea must have a cause. A cause
must be at least as perfect as its effect. So something at least as perfect as my
idea caused it. Therefore such a thing exists. But that thing must be perfect,
that is, God.
Suppose we grant Descartes the idea mentioned in the first premise.
(There are theological traditions that would not even do that. They would say
that God’s perfection defies understanding, so that we have no idea of it, or
him.) Still, why is he entitled to the premise that his idea must have a cause?
Might not there be events that have simply no cause? Events that, as we might
say, “just happen”? After all, sitting on his rock, Descartes cannot appeal to any
normal, scientific, experience. In his bare metaphysical solitude, how can he
deny that events might just happen? And if he thinks the contrary, shouldn’t he
then worry whether the Demon might be working on him, making him think
this although it is not true?
However, it gets worse when we arrive at the next step. Consider my
idea of someone who is perfectly punctual. Does this need a perfectly punctual
cause? Surely a better thing to think would be this. I can simply define what it is
for someone to be perfectly punctual. It means that they are never late (or
perhaps, never early and never late). To understand what it would be for
someone to be like that, I do not have to have come across such a person. I can
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describe them in advance. I understand what condition they have to satisfy
without any such acquaintance, and indeed even if nobody is ever like that.
Probably Descartes would reject the analogy. Perhaps he thinks of it
more like this. Do I have an idea of a perfect mathematician? Well, I can start by
thinking of a mathematician as one who never makes mistakes. But that is
hardly adequate. A perfect mathematician would be imaginative and inventive
as well. Now, with my very limited knowledge of mathematics, I only have a
very confused understanding of what that would be like. In general, I cannot
clearly comprehend or understand inventions before they come along -otherwise, I would be making the inventions myself! So perhaps it would take
a perfect mathematician to give me a good idea (a “clear and distinct” idea) of
what a perfect mathematician would be like.
Well, perhaps; but now it becomes doubtful whether I do have a clear
and distinct idea of a perfect mathematician, and analogously, of a perfect
being. Generally, what happens if I frame this idea is that I think more as I did
when thinking of someone perfectly punctual. I think of an agent who never
makes mistakes, never behaves unkindly, never finds things he cannot do, and
so on. I might add in imagination something like a kind of glow, but it is clear
that this will not help. It surely seems presumptuous, or even blasphemous, to
allow myself a complete, clear, comprehension of God’s attributes.
In fact, elsewhere in his writings Descartes gives a rather lovely analogy,
but one which threatens to undermine the trademark argument:
[W]e can touch a mountain with our hands but we cannot put our arms
around it as we could put them around a tree or something else not too
large for them. To grasp something is to embrace it in one’s thought; to
know something it is sufficient to touch it with one’s thought.
Perhaps we can only touch God’s supposed qualities by way of definition, but
cannot comprehend them. In that case we cannot argue back to an ideal or
archetype that enabled us to comprehend them.
So, the trademark argument is one that strikes most of us as far from
demon-proof — so far, in fact, that it seems pretty easy to resist even if we are
not at all in the grip of extreme doubt. At this point some suppressed premises
suggested by the history of ideas may be used to excuse Descartes. He was
undoubtedly more optimistic about the trademark argument than we can be
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because he inherited a number of ideas from previous philosophical traditions.
One very important one is that genuine causation is a matter of the cause
passing on something to an effect. Causation is like passing the baton in a relay
race. So, for example, it takes heat to make something hot, or movement to
induce motion. This is a principle that surfaces again and again in the history of
philoso-phy, and we shall encounter it more than once. Here it disposed
Descartes to think that the “perfection” in his idea needed to be secreted into
it, as it were, by a perfect cause.
But this principle about causation is scarcely demon-proof. In fact, it is
not even true. We have become familiar with causes that bear no resemblance
to their effects. The movement of a piece of iron in a magnetic field bears no
resemblance to an electric cur-rent, but that is what it causes. In fact, it seems
as though Descartes (once more influenced by ideas from previous
philosophical traditions) may have slipped into thinking that an idea of X
actually shares X. So an idea of infinity, for instance, would be an infinite idea.
(Would an idea of something solid be a solid idea?) Similarly an idea of
perfection would be a perfect idea, and would require a perfect cause. But
again, it might be the Demon that makes you think any such thing, and again
there is no good reason to follow him.
The Cartesian Circle
Descartes convinced himself that the argument was good: every step in it was
“clear and distinct”. So now he has God, and God is no deceiver. Still, remember
that to do this he had to trust his clear and distinct ideas as sources of truth.
Nevertheless, isn’t there an awful hole in his procedure? What happened to the
Demon? Might not even our clear and distinct ideas lead us astray? To close off
this possibility, it seems, Descartes turns round and uses God — the God whose
existence he has just proved — as the guarantor that what we perceive clearly
and distinctly must be true.
It was one of his contemporaries, Antoine Arnauld (1612-94), who cried
“foul” most loudly at this point, accusing Descartes of arguing in a circle, the
infamous “Cartesian circle”. Descartes seems committed to two different
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priorities. Consider the view that if we clearly and distinctly perceive some
proposition p, then it is true that p. Let us abbreviate this to (CDp -» Tp), reading
that if p is clear and distinct (“CD”), then it is true (“T”). And suppose we
symbolize “God exists and does not deceive us” by “G”. Then the circle is that
at some points it seems that Descartes holds: I can know that (CDp -» Tp) only
if I first know G. But at other points he holds: I can know that G only if I first
know (CDp -» Tp). It is like the familiar impasse in the morning, when you need
to have some coffee to get out of bed, and you need to get out of bed to fix
the coffee.
One or the other has to come first. There is a whole literature trying to
understand whether Descartes actually falls into this trap. Some commentators
cite passages in which it seems that he does not really hold the first. The major
suggestion is that G is necessary only to validate memory of proofs. So while
you actually clearly and distinctly perceive something, you do not need to trust
anything at all, even G, to be entitled to assert its truth. But later, when you
have forgotten the proof, only G underwrites your title to say that you once
proved it, so it must be true.
Other commentators suggest that Descartes does not need the second.
He sees that God exists, clearly and distinctly, but does not need a general rule,
of the kind (CDp -» Tp), to underwrite this perception. He can be certain of this
instance of the rule, without being sure about the rule itself. This is itself an
interesting form of suggestion, and introduces a very important truth, which is
that very often we are more certain of particular verdicts than we are of the
principles that we might cite when we try to defend them. For example, I might
know that a particular sentence is grammatical, without being sure of any
general rule of grammar that allows it. Philosophers have often been rather
hard on this possibility. The admired character Socrates, in Plato’s Dialogues, is
infuriatingly fond of getting his stooges to say something, showing that they
cannot defend it by articulate general principles, and concluding that they
didn’t really have any right to claim what they did. However, the case of
grammatical knowledge suggests that this is a bad inference. Consider as well
how in perception, I may recognize something as a Pomeranian, or a member
of the Rolling Stones, or my wife, without knowing any general principles that
“justify” the verdict. My perceptual system may operate according to some
general principles or “algorithms” for translating visual input into verdicts, but
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I have no idea what they are. So I couldn’t answer a Socrates who asked for
general principles underlying my recognition. I could only flounder and splutter.
But I recognize the Pomeranian, or Rolling Stone, or my wife, for all that.
Socrates’ procedure is only apt to give philosophers a bad name.
Still, we are bound to ask why Descartes thinks he can be certain of this
instance of the rule. Why is his “seeing” that God exists clearly and distinctly
also a clear and distinct case of seeing the truth? Some of us may have the dark
suspicion that it is because mention of God clouds the mind rather than
clarifying it.
For our purposes, we can leave this issue. What remains clear is that
there is a distinct whiff of double standards here. The kind of sceptical problem
embodied in the Evil Demon is somehow quietly forgotten, while Descartes
tries to engineer his way off the lonely rock of the Cogito. And this might
suggest that he has put himself on a desert island from which there is no
escape.
Foundations and Webs
The great Scottish thinker David Hume (1711-76) criticized Descartes like this:
There is a species of scepticism, antecedent to all study and philosophy,
which is much inculcated by Descartes and others, as a sovereign
preservative against error and precipitate judgment. It recommends an
universal doubt, not only of all our former opinions and principles, but also
of our very faculties; of whose veracity, say they, we must assure
ourselves, by a chain of reasoning, deduced from some original principle,
which cannot possibly be fallacious or deceitful. But neither is there any
such original principle, which has a prerogative above others, that are selfevident and convincing. Or if there were, could we advance a step beyond
it, but by the use of those very faculties, of which we are supposed to be
already diffident. The Cartesian doubt, therefore, were it ever possible to
be attained by any human creature (as it plainly is not) would be entirely
incurable; and no reasoning could ever bring us to a state of assurance and
conviction upon any subject.
If Descartes’s project is to use reason to fend off universal doubt about the
truthfulness of reason, then it has to fail.
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Hume’s challenge seems convincing. It looks as though Descartes was
doomed to failure. So what should be the outcome? General scepticism,
meaning pessimism about whether there is any harmony at all between the way
we believe things to be and the way they are? Or something else? Other
possibilities need introduction.
One way of thinking — Hume’s own — accepts the view that our system
of belief needs some kind of foundation. However, it denies that that
foundation could have the kind of rational status that Descartes wanted. The
veracity (truthfulness) of our senses and reasonings is itself part of the
foundation. It cannot itself be demonstrated by standing on some other
“original principle”. For all of us, outside the philosophical study, it comes
naturally to trust our common experience. We grow up doing so, and as we
grow up we become good at recognizing danger areas (illusions, mirages)
against the background of natural beliefs we all form. The self-corrective nature
of our systems of belief, mentioned above, is all we need. We could call this
approach non-rational or natural foundationalism. (Not of course implying that
there is anything irrational about it. It is just that the things in the foundation
do not have the demon-proof way of “standing to reason” that Descartes had
hoped for.) Hume himself gave a number of arguments for side-lining any
appeal to rationality, and we visit some of them in due course.
The emphasis on natural ways of forming belief chimes in with another
strand in Hume and other British philosophers of the seventeenth and
eighteenth centuries, which is their distrust of the power of unaided reason.
For these philosophers, the best contact between mind and the world is not
the point at which a mathematical proof crystallizes, but the point at which you
see and touch a familiar object. Their paradigm was knowledge by sense
experience rather than by reason. Because of this, they are labelled empiricists,
whereas Descartes is a card-carrying rationalist. The labels, however, conceal a
lot of important detail. For example, at some points when he gets under
pressure, Descartes himself appears to say that the really good thing about
clear and distinct ideas is that you can’t doubt them when you have them. This
is not really a certification by reason, so much as the very same kind of natural
potency that Hume himself attaches to basic empirical beliefs. And soon we
visit an area where the champion of British empiricism, John Locke (1632-1704),
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is as rationalist as the best of them. Great philosophers have a disturbing habit
of resisting labelling.
On this view, Descartes’s problem was that he relied too much on the
powers of reason. Instead, we can appeal to nature, here meaning our natural
propensities to form beliefs and to correct them. And what of the Evil Demon?
On this story, the true moral of Descartes’s struggles is that if we raise the
question whether our experience and reasoning (en bloc) accords with the way
the world is (en bloc), it will take an act of faith to settle it. “God” simply labels
whatever it is that ensures this harmony between belief and the world. But, as
Hume says in the passage just quoted, we do not find a need to raise this
question in normal life. The hyperbolic doubt, and the answer to it, is in this
sense unreal.
This may sound sensible, or it may just sound complacent. But to blunt
the charge of complacency, we can at least notice this. Regarding the doubt as
unreal does not have to mean that we simply turn our backs on the problem of
harmony between appearance and reality: how we think and how things are.
We can approach it from within our normal framework of beliefs. In fact, when
Hume himself approached it in this way, he became overwhelmed by difficulties
in our ordinary ways of thinking about things: difficulties strong enough to
reintroduce scepticism about our ability to know anything about the world. This
is the topic of Chapter 7.
However, one piece of optimism is available to us, two centuries later.
We might thus suppose that evolution, which is presumably responsible for the
fact that we have our senses and our reasoning capacities, would not have
selected for them (in the shape in which we have them) had they not worked.
If our eyesight, for example, did not inform us of predators, food, or mates just
when predators, food, and mates are about, it would be of no use to us. So it is
built to get these things right. The harmony between our minds and the world
is due to the fact that the world is responsible for our minds. Their function is
to represent it so that we can meet our needs; if they were built to represent it
in any way other than the true way, we could not survive. This is not an
argument designed to do away with the Evil Demon. It is an argument that
appeals to things we take ourselves to know about the world. Unfortunately,
we have to visit in time the area of Hume’s doubts, where things we take
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ourselves to know about the world also serve to make that knowledge seem
doubtful.
A rather different response shrugs off the need for any kind of
“foundations”, whether certified by reason, as Descartes hoped, or merely
natural, as in Hume. This approach goes back to emphasizing instead the
coherent structure of OUR everyday system of beliefs: the way they hang
together, whereas the sporadic experiences or beliefs we get in dreams are
fragmentary and incoherent. It then points out an interesting feature of
coherent structures, namely that they do not need foundations. A ship or a web
may be made up of a tissue of interconnecting parts, and it derives its strength
from just those interconnections. It does not need a “base” or a “starting point”
or “foundation”. A structure of this kind can have each bit supported by other
bits without there being any bit that supports all the others without support
itself. Similarly, if any one belief is challenged, others can support it, unless, of
course, it turns out that nothing else supports it, in which case it should be
dropped. The Austrian philosopher Otto Neurath (1882-1945) used this lovely
metaphor for our body of knowledge:
We are like sailors who on the open sea must reconstruct their ship but are
never able to start afresh from the bottom.
Any part can be replaced, provided there is enough of the rest on which to
stand. But the whole structure cannot be challenged en bloc, and if we try to
do so, we find ourselves on Descartes’s lonely rock.
This approach is usually called “coherentism”. Its motto is that while
every argument needs premises, there is nothing that is the premise of every
argument. There is no foundation on which everything rests. Coherentism is
nice in one way, but dissatisfying in another. It is nice in what it does away with,
namely the elusive foundations. It is, however, not clear that it offers us enough
to replace them. This is because we seemed able to understand the possibility
represented by the Evil Demon — that our system of belief should be extensive
and coherent and interlocking, but all completely wrong. As I said in the
introduction to this chapter, even as children we fall naturally into wondering
whether all experience might be a dream. We might sympathize with
Descartes’s thought that if the options are coherentism or scepticism, the more
honest option would be scepticism.
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It is good, then, to remember four options in epistemology (the theory
of knowledge). There is rational foundationalism, as attempted by Descartes.
There is natural foundationalism, as attempted in Hume. There is coherentism.
And brooding over all of them, there is scepticism, or the view that there is no
knowledge. Each of these has had distinguished defenders. Whichever the
reader prefers, he or she will find good philosophical company. One might think
that Descartes got almost everything right, or that he got almost everything
wrong. The baffling thing is to defend whichever answer commends itself.
Local Scepticisms
Scepticism can be raised in particular areas, as well as in the global fashion of
Descartes. Someone might be convinced that we have, say, scientific
knowledge, but be very doubtful about knowledge in ethics or politics or
literary criticism. We find particular areas shortly where it does not take
hyperbolic doubt, only a bit of caution, for us to become insecure. However,
there are other nice examples of highly general areas where scepticism is
baffling. The philosopher Bertrand Russell (1872-1970) considered the example
of time. How do I know that the world did not come into existence a very few
moments ago, but complete with delusive traces of a much greater age? Those
traces would include, of course, the modifications of the brain that give us what
we take to be memories. They would also include all the other things that we
interpret as signs of great age. In fact, Victorian thinkers struggling to reconcile
the biblical account of the history of the world with the fossil record had already
suggested much the same thing about geology. On this account, around 4,000
years ago God laid down all the misleading evidence that the earth is about
4,000 million years old (and, we can now add, misleading signs that the
universe is about 13,000 million years old). This was never a popular move,
probably because if you are sceptical about time, you quickly become sceptical
about everything, or maybe because it presents God as something like a largescale practical joker. Russell’s possibility sounds almost as far-fetched as
Descartes’s Evil Demon.
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However, there is one highly intriguing thing about Russell’s scenario.
This is that it can actually be argued to be scientifically more probable than the
alternative we all believe in! This is because science tells us that “low-entropy”
or, in other words, highly ordered systems are more improbable. In addition, as
physical systems like the cosmos evolve, entropy or disorder increases. The
smoke never returns into the cigarette; the toothpaste never goes back into
the tube. The extraordinary thing is that there was ever enough order in things
for the smoke to be in the cigarette or the toothpaste to be in the tube in the
first place. So, one might argue, it is “easier” for a moderately disordered world,
such as the world is now, to come into existence, than it is for any lowerentropy, more orderly ancestor. Intuitively, it is as if there are more ways this
can happen, just as there are more ways you can get four-letter or five-letter
words in an initial hand of seven letters in Scrabble, than there are in which you
can get a seven-letter word. It is much more probable that you get a four-letter
word than a seven-letter word. Similarly, the argument goes, it is as if God or
Nature had less to do, to make the world as it is today out of nothing, than to
make the lower-entropy world as it is supposed to have been some thirteen
billion years ago out of nothing. Therefore, it is more probable that it happened
like that. In a straight competition for probability between Russell’s outlandish
hypothesis and common sense, Russell wins. I leave this for the reader to
ponder.
The Moral
How then should we regard knowledge? Knowledge implies authority: the
people who know are the people to whom we should listen. It implies reliability:
the people who know are those who are reliable at registering the truth, like
good instruments. To claim knowledge implies claiming a sense of our own
reliability. And to accord authority to someone or some method involves seeing
it as reliable. The unsettling scenarios of a Descartes or a Russell unseat our
sense of our own reliability. Once we have raised the outlandish possibilities,
our sense of a reliable connection between the way things are and the ways we
take them to be goes dim. We could regain it, if we could argue that the
scenarios are either impossible, or at least have no real chance of being the way
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things are. The difficulty is that it is hard to show them to be impossible, and in
these abstract realms we have no very good sense of probabilities or chances.
So it is difficult to argue that they have no chance of being true without relying
on the very opinions that they query. Hence, scepticism permanently beckons,
or threatens, us. We may be tracking the world reliably, but we may not. To
revert to the engineering analogy I used in the Introduction, the structure of
our thought seems to span large gaps: here, the gap between how things
appear and how they might be. We hand ourselves the right to cross those
gaps. But if we do this trailing no very good sense of our own reliability or
harmony with the truth, then that right seems ill-founded. And this is what the
sceptic insists upon. Any confidence in a harmony between the way we take
things to be, and the way they are, will seem to be a pure act of faith.
Descartes left us with a problem of knowledge. He also left us with
severe problems in understanding the place of our minds in nature. And finally
the entire scientific revolution of which he was such a distinguished parent left
us with profound problems of understanding the world in which we are placed.
We have seen something of the problem of knowledge. The next chapter turns
to problems of mind…
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Appearance and Reality1
by Bertrand Russell, 1912
English Analytic Philosopher
Is there any knowledge in the world which is so certain that no reasonable man
could doubt it? This question, which at first sight might not seem difficult, is
really one of the most difficult that can be asked. When we have realized the
obstacles in the way of a straightforward and confident answer, we shall be
well launched on the study of philosophy — for philosophy is merely the attempt
to answer such ultimate questions, not carelessly and dogmatically, as we do in
ordinary life and even in the sciences, but critically after exploring all that makes
such questions puzzling, and after realizing all the vagueness and confusion
that underlie our ordinary ideas.
In daily life, we assume as certain many things which, on a closer
scrutiny, are found to be so full of apparent contradictions that only a great
amount of thought enables us to know what it is that we really may believe. In
the search for certainty, it is natural to begin with our present experiences, and
in some sense, no doubt, knowledge is to be derived from them. But any
statement as to what it is that our immediate experiences make us know is very
likely to be wrong. It seems to me that I am now sitting in a chair, at a table of
a certain shape, on which I see sheets of paper with writing or print. By turning
my head I see out of the window buildings and clouds and the sun. I believe that
the sun is about ninety-three million miles from the earth; that it is a hot globe
many times bigger than the earth; that, owing to the earth’s rotation, it rises
every morning, and will continue to do so for an indefinite time in the future. I
believe that, if any other normal person comes into my room, he will see the
same chairs and tables and books and papers as I see, and that the table which
I see is the same as the table which I feel pressing against my arm. All this seems
to be so evident as to be hardly worth stating, except in answer to a man who
doubts whether I know anything. Yet all this may be reasonably doubted, and
1
From Russell’s 1912 Problems of Philosophy, chapter 1.
Russell 1912: “Appearance & Reality”
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all of it requires much careful discussion before we can be sure that we have
stated it in a form that is wholly true.
To make our difficulties plain, let us concentrate attention on the table.
To the eye it is oblong, brown and shiny, to the touch it is smooth and cool and
hard; when I tap it, it gives out a wooden sound. Any one else who sees and
feels and hears the table will agree with this description, so that it might seem
as if no difficulty would arise; but as soon as we try to be more precise our
troubles begin. Although I believe that the table is ‘really’ of the same colour all
over, the parts that reflect the light look much brighter than the other parts,
and some parts look white because of reflected light. I know that, if I move, the
parts that reflect the light will be different, so that the apparent distribution of
colours on the table will change. It follows that if several people are looking at
the table at the same moment, no two of them will see exactly the same
distribution of colours, because no two can see it from exactly the same point
of view, and any change in the point of view makes some change in the way the
light is reflected.
For most practical purposes these differences are unimportant, but to
the painter they are all-important: the painter has to unlearn the habit of
thinking that things seem to have the colour which common sense says they
‘really’ have, and to learn the habit of seeing things as they appear. Here we
have already the beginning of one of the distinctions that cause most trouble
in philosophy — the distinction between ‘appearance’ and ‘reality’, between
what things seem to be and what they are. The painter wants to know what
things seem to be, the practical man and the philosopher want to know what
they are; but the philosopher’s wish to know this is stronger than the practical
man’s, and is more troubled by knowledge as to the difficulties of answering
the question.
To return to the table. It is evident from what we have found, that there
is no colour which preeminently appears to be the colour of the table, or even
of any one particular part of the table — it appears to be of different colours
from different points of view, and there is no reason for regarding some of
these as more really its colour than others. And we know that even from a given
point of view the colour will seem different by artificial light, or to a colour-blind
man, or to a man wearing blue spectacles, while in the dark there will be no
Russell 1912: “Appearance & Reality”
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colour at all, though to touch and hearing the table will be unchanged. This
colour is not something which is inherent in the table, but something
depending upon the table and the spectator and the way the light falls on the
table. When, in ordinary life, we speak of the colour of the table, we only mean
the sort of colour which it will seem to have to a normal spectator from an
ordinary point of view under usual conditions of light. But the other colours
which appear under other conditions have just as good a right to be considered
real; and therefore, to avoid favouritism, we are compelled to deny that, in
itself, the table has any one particular colour.
The same thing applies to the texture. With the naked eye one can see
the gram, but otherwise the table looks smooth and even. If we looked at it
through a microscope, we should see roughnesses and hills and valleys, and all
sorts of differences that are imperceptible to the naked eye. Which of these is
the ‘real’ table? We are naturally tempted to say that what we see through the
microscope is more real, but that in turn would be changed by a still more
powerful microscope. If, then, we cannot trust what we see with the naked eye,
why should we trust what we see through a microscope? Thus, again, the
confidence in our senses with which we began deserts us.
The shape of the table is no better. We are all in the habit of judging as
to the ‘real’ shapes of things, and we do this so unreflectingly that we come to
think we actually see the real shapes. But, in fact, as we all have to learn if we
try to draw, a given thing looks different in shape from every different point of
view. If our table is ‘really’ rectangular, it will look, from almost all points of
view, as if it had two acute angles and two obtuse angles. If opposite sides are
parallel, they will look as if they converged to a point away from the spectator;
if they are of equal length, they will look as if the nearer side were longer. All
these things are not commonly noticed in looking at a table, because
experience has taught us to construct the ‘real’ shape from the apparent shape,
and the ‘real’ shape is what interests us as practical men. But the ‘real’ shape is
not what we see; it is something inferred from what we see. And what we see
is constantly changing in shape as we, move about the room; so that here again
the senses seem not to give us the truth about the table itself, but only about
the appearance of the table.
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Similar difficulties arise when we consider the sense of touch. It is true
that the table always gives us a sensation of hardness, and we feel that it resists
pressure. But the sensation we obtain depends upon how hard we press the
table and also upon what part of the body we press with; thus the various
sensations due to various pressures or various parts of the body cannot be
supposed to reveal directly any definite property of the table, but at most to be
signs of some property which perhaps causes all the sensations, but is not
actually apparent in any of them. And the same applies still more obviously to
the sounds which can be elicited by rapping the table.
Thus it becomes evident that the real table, if there is one, is not the
same as what we immediately experience by sight or touch or hearing. The real
table, if there is one, is not immediately known to us at all, but must be an
inference from what is immediately known. Hence, two very difficult questions
at once arise; namely, (1) Is there a real table at all? (2) If so, what sort of object
can it be?
It will help us in considering these questions to have a few simple terms
of which the meaning is definite and clear. Let us give the name of ‘sense-data’
to the things that are immediately known in sensation: such things as colours,
sounds, smells, hardnesses, roughnesses, and so on. We shall give the name
‘sensation’ to the experience of being immediately aware of these things. Thus,
whenever we see a colour, we have a sensation of the colour, but the colour
itself is a sense-datum, not a sensation. The colour is that of which we are
immediately aware, and the awareness itself is the sensation. It is plain that if
we are to know anything about the table, it must be by means of the sense-data
— brown colour, oblong shape, smoothness, etc. — which we associate with the
table; but, for the reasons which have been given, we cannot say that the table
is the sense-data, or even that the sense-data are directly properties of the
table. Thus a problem arises as to the relation of the sense-data to the real
table, supposing there is such a thing.
The real table, if it exists, we will call a ‘physical object’. Thus we have to
consider the relation of sense-data to physical objects. The collection of all
physical objects is called ‘matter’. Thus our two questions may be re-stated as
follows: (1) Is there any such thing as matter? (2) If so, what is its nature?
Russell 1912: “Appearance & Reality”
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The philosopher who first brought prominently forward the reasons for
regarding the immediate objects of our senses as not existing independently of
us was Bishop Berkeley (1685-1753). His Three Dialogues between Hylas and
Philonous, in Opposition to Sceptics and Atheists, undertake to prove that
there is no such thing as matter at all, and that the world consists of nothing
but minds and their ideas. Hylas has hitherto believed in matter, but he is no
match for Philonous, who mercilessly drives him into contradictions and
paradoxes, and makes his own denial of matter seem, in the end, as if it were
almost common sense. The arguments employed are of very different value:
some are important and sound, others are confused or quibbling. But Berkeley
retains the merit of having shown that the existence of matter is capable of
being denied without absurdity, and that if there are any things that exist
independently of us they cannot be the immediate objects of our sensations.
There are two different questions involved when we ask whether
matter exists, and it is important to keep them clear. We commonly mean by
‘matter’ something which is opposed to ‘mind’, something which we think of
as occupying space and as radically incapable of any sort of thought or
consciousness. It is chiefly in this sense that Berkeley denies matter; that is to
say, he does not deny that the sense-data which we commonly take as signs of
the existence of the table are really signs of the existence of something
independent of us, but he does deny that this something is nonmental, that it
is neither mind nor ideas entertained by some mind. He admits that there must
be something which continues to exist when we go out of the room or shut our
eyes, and that what we call seeing the table does really give us reason for
believing in something which persists even when we are not seeing it. But he
thinks that this something cannot be radically different in nature from what we
see, and cannot be independent of seeing altogether, though it must be
independent of our seeing. He is thus led to regard the ‘real’ table as an idea in
the mind of God. Such an idea has the required permanence and independence
of ourselves, without being — as matter would otherwise be — something quite
unknowable, in the sense that we can only infer it, and can never be directly
and immediately aware of it.
Other philosophers since Berkeley have also held that, although the
table does not depend for its existence upon being seen by me, it does depend
upon being seen (or otherwise apprehended in sensation) by some mind — not
Russell 1912: “Appearance & Reality”
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necessarily the mind of God, but more often the whole collective mind of the
universe. This they hold, as Berkeley does, chiefly because they think there can
be nothing real — or at any rate nothing known to be real except minds and their
thoughts and feelings. We might state the argument by which they support
their view in some such way as this: ‘Whatever can be thought of is an idea in
the mind of the person thinking of it; therefore nothing can be thought of
except ideas in minds; therefore anything else is inconceivable, and what is
inconceivable cannot exist.’
Such an argument, in my opinion, is fallacious; and of course those who
advance it do not put it so shortly or so crudely. But whether valid or not, the
argument has been very widely advanced in one form or another; and very
many philosophers, perhaps a majority, have held that there is nothing real
except minds and their ideas. Such philosophers are called ‘idealists’. When
they come to explaining matter, they either say, like Berkeley, that matter is
really nothing but a collection of ideas, or they say, like Leibniz (1646-1716), that
what appears as matter is really a collection of more or less rudimentary minds.
But these philosophers, though they deny matter as opposed to mind,
nevertheless, in another sense, admit matter. It will be remembered that we
asked two questions; namely, (1) Is there a real table at all? (2) If so, what sort
of object can it be? Now both Berkeley and Leibniz admit that there is a real
table, but Berkeley says it is certain ideas in the mind of God, and Leibniz says it
is a colony of souls. Thus both of them answer our first question in the
affirmative, and only diverge from the views of ordinary mortals in their answer
to our second question. In fact, almost all philosophers seem to be agreed that
there is a real table. they almost all agree that, however much our sense-data – colour, shape, smoothness, etc. — may depend upon us, yet their occurrence
is a sign of something existing independently of us, something differing,
perhaps, completely from our sense-data whenever we are in a suitable relation
to the real table.
Now obviously this point in which the philosophers are agreed — the
view that there is a real table, whatever its nature may be is vitally important,
and it will be worth while to consider what reasons there are for accepting this
view before we go on to the further question as to the nature of the real table.
Russell 1912: “Appearance & Reality”
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Our next chapter, therefore, will be concerned with the reasons for supposing
that there is a real table at all.
Before we go farther it will be well to consider for a moment what it is
that we have discovered so far. It has appeared that, if we take any common
object of the sort that is supposed to be known by the senses, what the senses
immediately tell us is not the truth about the object as it is apart from us, but
only the truth about certain sense-data which, so far as we can see, depend
upon the relations between us and the object. Thus what we directly see and
feel is merely ‘appearance’, which we believe to be a sign of some
‘reality’ behind. But if the reality is not what appears, have we any means
of knowing whether there is any reality at all? And if so, have we any means of
finding out what it is like?
Such questions are bewildering, and it is difficult to know that even the
strangest hypotheses may not be true. Thus our familiar table, which has
roused but the slightest thoughts in us hitherto, has become a problem full of
surprising possibilities. The one thing we know about it is that it is not what it
seems. Beyond this modest result, so far, we have the most complete liberty of
conjecture. Leibniz tells us it is a community of souls: Berkeley tells us it is an
idea in the mind of God; sober science, scarcely less wonderful, tells us it is a
vast collection of electric charges in violent motion.
Among these surprising possibilities, doubt suggests that perhaps there
is no table at all. Philosophy, if it cannot answer so many questions as we could
wish, has at least the power of asking questions which increase the interest of
the world, and show the strangeness and wonder lying just below the surface
even in the commonest things of daily life.
Russell 1912: “Appearance & Reality”
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Meditations on First Philosophy (First Excerpt)
by René Descartes, 1641
Early Modern French Mathematician and Philosopher
Translated by John Cottingham, 1984
Meditation 1
Some years ago I was struck by the large number of falsehoods that I had
accepted as true in my childhood, and by the highly doubtful nature of the
whole edifice that I had subsequently based on them. I realized that it was
necessary, once in the course of my life, to demolish everything completely and
start again right from the foundations if I wanted to establish anything at all in
the sciences that was stable and likely to last. But the task looked an enormous
one, and I began to wait until I should reach a mature enough age to ensure
that no subsequent time of life would be more suitable for tackling such
inquiries. This led me to put the project off for so long that I would now be to
blame if by pondering over it any further I wasted the time still left for carrying
it out. So today I have expressly rid my mind of all worries and arranged for
myself a clear stretch of free time. I am here quite alone, and at last I will devote
myself sincerely and without reservation to the general demolition of my
opinions.
But to accomplish this, it will not be necessary for me to show that all
my opinions are false, which is something I could perhaps never manage.
Reason now leads me to think that I should hold back my assent from opinions
which are not completely certain and indubitable just as carefully as I do from
those which are patently false. So, for the purpose of rejecting all my opinions,
it will be enough if I find in each of them at least some reason for doubt. And to
do this I will not need to run through them all individually, which would be an
endless task. Once the foundations of a building are undermined, anything built
Descartes 1641: Meditations (First Excerpt)
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on them collapses of its own accord; so I will go straight for the basic principles
on which all my former beliefs rested.
Whatever I have up till now accepted as most true I have acquired either
from the senses or through the senses. But from time to time I have found that
the senses deceive, and it is prudent never to trust completely those who have
deceived us even once.
Yet although the senses occasionally deceive us with respect to objects
which are very small or in the distance, there are many other beliefs about
which doubt is quite impossible, even though they are derived from the
senses—for example, that I am here, sitting by the fire, wearing a winter
dressing-gown, holding this piece of paper in my hands, and so on. Again, how
could it be denied that these hands or this whole body are mine? Unless perhaps
I were to liken myself to madmen, whose brains are so damaged by the
persistent vapors of melancholia that they firmly maintain they are kings when
they are paupers, or say they are dressed in purple when they are naked, or that
their heads are made of earthenware, or that they are pumpkins, or made of
glass. But such people are insane, and I would be thought equally mad if I took
anything from them as a model for myself.
A brilliant piece of reasoning! As if I were not a man who sleeps at night,
and regularly has all the same experiences1 while asleep as madmen do when
awake—indeed sometimes even more improbable ones. How often, asleep at
night, am I convinced of just such familiar events—that I am here in my
dressing-gown, sitting by the fire—when in fact I am lying undressed in bed!
Yet at the moment my eyes are certainly wide awake when I look at this piece
of paper; I shake my head and it is not asleep; as I stretch out and feel my hand
I do so deliberately, and I know what I am doing. All this would not happen with
such distinctness to someone asleep. Indeed! As if I did not remember other
occasions when I have been tricked by exactly similar thoughts while asleep! As
I think about this more carefully, I see plainly that there are never any sure signs
by means of which being awake can be distinguished from being asleep. The
result is that I begin to feel dazed, this very feeling only reinforces the notion
that I may be asleep.
Suppose then that I am dreaming, and that these particulars—that my eyes are
open, that I am moving my head and stretching out my hands—are not true.
Descartes 1641: Meditations (First Excerpt)
Page 2 of 6
Perhaps, indeed, I do not even have such hands or such a body at all.
Nonetheless, it must surely be admitted that the visions which come in sleep
are like paintings, which must have been fashioned in the likeness of things that
are real, and hence that at least these general kinds of things—eyes, head,
hands and the body as a whole—are things which are not imaginary but are real
and exist. For even when painters try to create sirens and satyrs with the most
extraordinary bodies, they cannot give them natures which are new in all
respects; they simply jumble up the limbs of different animals. Or if perhaps
they manage to think up something so new that nothing remotely similar has
ever been seen before—something which is therefore completely fictitious and
unreal—at least the colors used in the composition must be real. By similar
reasoning, although these general kinds of things—eyes, head, hands and so
on—could be imaginary, it must at least be admitted that certain other even
simpler and more universal things are real. These are as it were the real colors
from which we form all the images of things, whether true or false, that occur
in our thought.
This class appears to include corporeal nature in general, and its
extension; the shape of extended things; the quantity, or size and number of
these things; the place in which they may exist, the time through which they
may endure,2 and so on.
So a reasonable conclusion from this might be that physics, astronomy,
medicine, and all other disciplines which depend on the study of composite
things, are doubtful; while arithmetic, geometry and other subjects of this kind,
which deal only with the simplest and most general things, regardless of
whether they really exist in nature or not, contain something certain and
indubitable. For whether I am awake or asleep, two and three added together
are five, and a square has no more than four sides. It seems impossible that
such transparent truths should incur any suspicion of being false.
And yet firmly rooted in my mind is the long-standing opinion that there
is an omnipotent God who made me the kind of creature that I am. How do I
know that he has not brought it about that there is no earth, no sky, no
extended thing, no shape, no size, no place, while at the same time ensuring
that all these things appear to me to exist just as they do now? What is more,
just as I consider that others sometimes go astray in cases where they think
Descartes 1641: Meditations (First Excerpt)
Page 3 of 6
they have the most perfect knowledge, how do I know that God has not
brought it about that I too go wrong every time I add two and three or count
the sides of a square, or in some even simpler matter, if that is imaginable? But
perhaps God would not have allowed me to be deceived in this way, since he is
said to be supremely good. But if it were inconsistent with his goodness to have
created me such that I am deceived all the time, it would seem equally foreign
to his goodness to allow me to be deceived even occasionally; yet this last
assertion cannot be made.
Perhaps there may be some who would prefer to deny the existence of
so powerful a God rather than believe that everything else is uncertain. Let us
not argue with them, but grant them that everything said about God is a fiction.
According to their supposition, then, I have arrived at my present state by fate
or chance or a continuous chain of events, or by some other means; yet since
deception and error seem to be imperfections, the less powerful they make my
original cause, the more likely it is that I am so imperfect as to be deceived all
the time. I have no answer to these arguments, but am finally compelled to
admit that there is not one of my former beliefs about which a doubt may not
properly be raised; and this is not a flippant or ill-considered conclusion, but is
based on powerful and well thought-out reasons. So in the future I must
withhold my assent from these former beliefs just as carefully as I would from
obvious falsehoods, if I want to discover any certainty.
But it is not enough merely to have noticed this; I must make an effort
to remember it. My habitual opinions keep coming back, and, despite my
wishes, they capture my belief, which is as it were bound over to them as a
result of long occupation and the law of custom. I shall never get out of the
habit of confidently assenting to these opinions, so long as I suppose them to
be what in fact they are, namely highly probable opinions—opinions which,
despite the fact that they are in a sense doubtful, as has just been shown, it is
still much more reasonable to believe than to deny. In view of this, I think it will
be a good plan to turn my will in completely the opposite direction and deceive
myself, by pretending for a time that these former opinions are utterly false and
imaginary. I shall do this until the weight of preconceived opinion is counterbalanced and the distorting influence of habit no longer prevents my judgment
from perceiving things correctly. In the meantime, I know that no danger or
error will result from my plan, and that I cannot possibly go too far in my
Descartes 1641: Meditations (First Excerpt)
Page 4 of 6
distrustful attitude. This is because the task now in hand does not involve action
but merely the acquisition of knowledge.
I will suppose therefore that not God, who is supremely good and the
source of truth, but rather some malicious demon of the utmost power and
cunning has employed all his energies in order to deceive me. I shall think that
the sky, the air, the earth, colors, shapes, sounds and all external things are
merely the delusions of dreams which he has devised to ensnare my judgment.
I shall consider myself as not having hands or eyes, or flesh, or blood or senses,
but as falsely believing that I have all these things. I shall stubbornly and firmly
persist in this meditation; and, even if it is not in my power to know any truth, I
shall at least do what is in my power, that is, resolutely guard against assenting
to any falsehoods, so that the deceiver, however powerful and cunning he may
be, will be unable to impose on me in the slightest degree. But this is an arduous
undertaking, and a kind of laziness brings me back to normal life. I am like a
prisoner who is enjoying an imaginary freedom while asleep; as he begins to
suspect that he is asleep, he dreads being woken up, and goes along with the
pleasant illusion as long as he can. In the same way, I happily slide back into my
old opinions and dread being shaken out of them, for fear that my peaceful
sleep may be followed by hard labor when I wake, and that I shall have to toil
not in the light, but amid the inextricable darkness of the problems I have now
raised.
Meditation 2
So serious are the doubts into which I have been thrown as a result of
yesterday’s meditation that I can neither put them out of my mind nor see any
way of resolving them. It feels as if I have fallen unexpectedly into a deep
whirlpool which tumbles me around so that I can neither stand on the bottom
nor swim up to the top. Nevertheless I will make an effort and once more
attempt the same path which I started on yesterday. Anything which admits of
the slightest doubt I will set aside just as if I had found it to be wholly false; and
I will proceed in this way until I recognize something certain, or, if nothing else,
until I at least recognize for certain that there is no certainty. Archimedes used
Descartes 1641: Meditations (First Excerpt)
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to demand just one firm and immovable point in order to shift the entire earth;
so I too can hope for great things if I manage to find just one thing, however
slight, that is certain and unshakeable.
I will suppose then, that everything I see is spurious. I will believe that
my memory tells me lies, and that none of the things that it reports ever
happened. I have no senses. Body, shape, extension, movement and place are
chimeras. So what remains true? Perhaps just the one fact that nothing is
certain.
Yet apart from everything I have just listed, how do I know that there is
not something else which does not allow even the slightest occasion for doubt?
Is there not a God, or whatever I may call him, who puts into me the thoughts I
am now having? But why do I think this, since I myself may perhaps be the
author of these thoughts? In that case am not I, at least, something? But I have
just said that I have no senses and no body. This is the sticking point: what
follows from this? Am I not so bound up with a body and with senses that I
cannot exist without them? But I have convinced myself that there is absolutely
nothing in the world, no sky, no earth, no minds, no bodies. Does it now follow
that I too do not exist? No: if I convinced myself of something7 then I certainly
existed. But there is a deceiver of supreme power and cunning who is
deliberately and constantly deceiving me. In that case I too undoubtedly exist,
if he is deceiving me; and let him deceive me as much as he can, he will never
bring it about that I am nothing so long as I think that I am something. So after
considering everything very thoroughly, I must finally conclude that this
proposition, I am, I exist, is necessarily true whenever it is put forward by me or
conceived in my mind…
Descartes 1641: Meditations (First Excerpt)
Page 6 of 6
The Case for Torture1
by Michael Levin, 1983
Professor of Philosophy at City University of New York (CUNY)
It is generally assumed that torture is impermissible, a throwback to a more
brutal age. Enlightened societies reject it outright, and regimes suspected of
using it risk the wrath of the United States.
I believe this attitude is unwise. There are situations in which torture is
not merely permissible but morally mandatory. Moreover, these situations are
moving from the realm of imagination to fact.
Death: Suppose a terrorist has hidden an atomic bomb on Manhattan
Island which will denotate on noon July 4 unless… (here follow the usual
demands for money and release of his friends from jail). Suppose, further, that
he is caught at 10am of the fateful day, but – preferring death to failure – won’t
disclose where the bomb is. What do we do? If we follow due process – wait for
his lawyer, arraign him – millions of people will die. If the only way to save those
lives is to subject the terrorist to the most excruciating possible pain, what
grounds can there be for not doing so? I suggest there are none. In any case, I
ask you to face the question with an open mind.
Torturing the terrorist is unconstitutional? Probably. But millions of lives
surely outweigh constitutionality. Torture is barbaric? Mass murder is far more
barbaric. Indeed, letting millions of innocents die in deference to one who
flaunts his guilt is moral cowardice, an unwillingness to dirty one’s hands. If you
caught the terrorist, could you sleep nights knowing that millions died because
you couldn’t bring yourself to apply the electrodes?
Once you concede that torture is justified in extreme cases, you have
admitted that the decision to use torture is a matter of balancing innocent lives
against the means needed to save them. You must now face more realistic
cases involving more modest numbers. Someone plants a bomb on a jumbo jet.
1
Originally published in Newsweek, 7 June 1983, p. 13
Levin 1983: “The Case for Torture”
Page 1 of 3
He alone can disarm it, and his demands cannot be met (or if they can, we
refuse to set a precedent by yielding to his threats). Surely we can, we must, do
anything to the extortionist to save the passengers. How can we tell 300, or
100, or 10 people who never asked to be put in danger, “I’m sorry, you’ll have
to die in agony, we just couldn’t bring ourselves to…”
Here are the results of an informal poll about a third, hypothetical, case.
Suppose a terrorist group kidnapped a newborn baby from a hospital. I asked
four mothers if they would approve of torturing kidnappers if that were
necessary to get their own newborns back. All said yes, the most ‘liberal’ adding
that she would like to administer it herself.
I am not advocating torture as punishment. Punishment is addressed to
deeds irrevocably past. Rather, I am advocating torture as an acceptable
measure for preventing future evils. So understood, it is far less objectionable
than many extant punishments. Opponents of the death penalty, for example,
are forever insisting that executing a murderer will not bring back his victim (as
if the purpose of capital punishment were supposed to be resurrection, not
deterrence or retribution). But torture, in the cases described, is intended not
to bring anyone back but to keep innocents from being dispatched. The most
powerful argument against using torture as a punishment or to secure
confessions is that such practices disregard the rights of the individual. Well, if
the individual is all that important – and he is – it is correspondingly important
to protect the rights of individuals threatened by terrorists. If life is so valuable
that it must never been taken, the lives of the innocents must be saved even at
the price of hurting the one who endangers them.
Better precedents for torture are assassination and pre-emptive attack.
No Allied leader would have flinched at assassinating Hitler, had that been
possible. (The Allies did assassinate Heydrich.) Americans would be angered to
learn that Roosevelt could have had Hitler killed in 1943 – thereby shortening
the war and saving millions of lives – but refused on moral grounds. Similarly, if
nation A learns that nation B is about to launch an unprovoked attack, A has a
right to save itself by destroying B’s military capability first. In the same way, if
the police can by torture save those who would otherwise die at the hands of
kidnappers or terrorists, they must.
Levin 1983: “The Case for Torture”
Page 2 of 3
Idealism: There is an important difference between terrorists and their
victims that should mute talk of the terrorists’ “rights.” The terrorist’s victims
are at risk unintentionally, not having asked to be endangered. But the terrorist
knowingly initiated his actions. Unlike his victims, he volunteered for the risks
of his deed. By threatening to kill for profit or idealism, he renounces civilized
standards, and he can have no complaint if civilization tries to thwart him by
whatever means necessary.
Just as torture is justified only to save lives (not exhort confessions or
recantations), it is justifiably administered only to those known to hold
innocent lives in their hands. Ah, but how can the authorities ever be sure that
they have the malefactor? Isn’t there a danger of error and abuse? Won’t We
turn into Them?
Questions like these are disingenuous in a world in which terrorists
proclaim themselves and perform for television. The name of their game is
public recognition. After all, you can’t very well intimidate a government into
releasing your freedom fighters unless you announce that it is your group that
has seized its embassy. ‘Clear guilt’ is difficult to define, but when 40 million
people see a group of masked gunman seize an airplane on the evening news,
there is not much question about who the perpetrators are. There will be hard
cases where the situation is murkier. Nonetheless, a line demarcating the
legitimate use of torture can be drawn. Torture only the obviously guilty, and
only for the sake of saving innocents, and the line between Us and Them will
remain clear.
There is little danger that the Western democracies will lose their way if
they choose to inflict pain as one way of preserving order. Paralysis in the face
of evil is the greater danger. Some day soon a terrorist will threaten tens of
thousands of lives, and torture will be the only way to save them. We had better
start thinking about this.
Levin 1983: “The Case for Torture”
Page 3 of 3
A Little Bit of Logic
by Louis Pojman, 2006
American Philosopher, 1935-2005
Basics of Argument Analysis
Philosophy is centered in the analysis and construction of arguments. We call
the study of arguments logic. Let us devote a little time to the rudiments of
logic. By argument we do not mean a verbal fight but a process of supporting
a thesis (called the conclusion) with reasons (called premises). An argument
consists of at least two declarative sentences (sometimes called propositions),
one of which (the conclusion) logically follows from the others (the
premises).The connection by which the conclusion follows from the premises
is called an inference:1
1
Pojman’s original diagram is similar but wouldn’t transfer to Word neatly. It is meant to depict
that, from proposition 1 and proposition 2 combining, they serve as premises from which
another proposition can be concluded.
Page 1 of 20
[Arguments come in perhaps three basic varieties: Deductive, Inductive, and
Abductive reasoning. All three have various sub-varieties. They are evaluated
slightly differently from one another.]
Deductive Reasoning
A valid deductive argument is one that follows a correct logical form, so that if
the premises are true, the conclusion must also be true. If the form is not a good
one, the argument is invalid. We say that a valid deductive argument preserves
truth. It does so in much the same way as a good refrigerator preserves food.
If the food is good, a good refrigerator will preserve it; but if the food is already
spoiled, the refrigerator will not make it good. The same is true with the
premises of a valid argument. If the statements are true and the form is correct,
the conclusion will be true; but if the premises are not true, a valid argument
will not guarantee a true conclusion. [Note that a deductive argument can be
valid but have false premises. A deductive argument can also have true
premises but be invalid.]
A classic example of a valid argument is the following:
1. Socrates is a man. [Premise]
2. All men are mortal. [Premise]
3. So, Socrates is mortal. [Conclusion]
To identity the form, let us look at conclusion (3) and identity the two
major components: a subject (S) and a predicate (P). Socrates is the subject
term, and mortal is the predicate term. Now return to the two premises and
identity these two terms in them. We discover that the two terms are
connected by a third term, man (or the plural men). We call this the middle term
(M).
The form of the argument is as follows:
Page 2 of 20
1. S is M.
2. All M are P.
3. So, S is P.
This is an example of a valid deductive form. If premises (1) and (2) are
true, we will always get a true conclusion by using this form. But notice how
easy it would be to get an invalid form. Change the order of the second premise
to read” All P are M.” Let the first premise read “My roommate is a mammal”
and the second premise read “All dogs are mammals.” What do you get?
1. My roommate, Sam Smith, is a mammal.
2. Dogs are mammals.
3. So, my roommate is a dog.
Regardless of how badly you might treat your roommate, the argument
has improper form and cannot yield a valid conclusion; it is invalid. Every
argument is either valid or invalid. Like a woman who cannot be a little pregnant,
an argument cannot be partly valid or invalid but must be completely one or the
other. By seeking to find counterexamples for argument forms, we can discover
which are the correct forms. (A full study of this requires a course in logic.)
Validity is not the only concept we need to examine; soundness is also
important. An argument can be valid but still unsound. An argument is sound if
it has a valid form and all its premises are true. If at least one premise is false,
the argument is unsound. Here is an example of a sound argument:
1. If Mary is a mother, she must be a woman.
2. Mary is a mother (for she has just given birth to a baby).
3. So, Mary is a woman.
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If Mary hasn’t given birth, then premise (2) is false, and the argument is
unsound [but still valid].
You should be aware of four other deductive argument forms: modus
ponens, modus tollens, disjunctive syllogism, and reductio ad absurdum. Here are
their forms:
Modus Ponens (MP) (Affirming the Antecedent)
1. If P, then Q.
2. P.
3. So, Q.
Modus Tollens (MT) (Denying the Consequent)
1. If P, then Q.
2. Not-Q.
3. So, Not-P.
Note in a hypothetical proposition (if P, then Q) the first term (the proposition
P) is called the antecedent and the second term (Q) the consequent. Both
affirming the antecedent and denying the consequent yield valid forms.
Disjunctive Syllogism (DS) (Denying the Disjunct)
1. Either P or Q.
2. Not-Q. 3.
3. So, P.
Reductio ad Absurdum (RAA) (Reducing to a Contradiction)
1. Assume A. (A is the logical opposite of the conclusion you seek to
prove.)
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2. Logically deduce a contradiction from A. (This shows that A implies a
contradiction.)
3. This proves A is false, since a contradiction cannot be true. So not-A
must be true.
We have already given an example of a modus ponens:
1. If Mary is a mother, she must be a woman.
2. Mary is a mother.
3. So, Mary is a woman.
Here is an example of a modus tollens:
1. If Leslie is a mother, she is a woman.
2. Leslie is not a woman (but a man).
3. So, Leslie is not a mother.
Here is an example of a disjunctive syllogism (sometimes called “denying the
disjunct” – a disjunct refers to a proposition with an “or” statement in it, such
as “P or Q”):
1. John is either a bachelor or a married man.
2. We know for…