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\title {Descartes \\ Lecture 10}

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Lecture 10:

Descartes

[email protected]

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Is there a Cartesian Circle?

\section{Is there a Cartesian Circle?}

How do I know that what I clearly and distinctly perceive is true?

1. God exists.

2. God is the ultimate source of these perceptions.

3. God does not deceive.

Some passages suggest the God-first idea

‘[F]rom this contemplation of the true God ... I think I can see a way forward to the knowledge of other things. To begin with, I recognize that it is impossible that God should ever deceive me. . . . And since God does not wish to deceive me, he surely did not give me the kind of faculty which would ever enable me to go wrong while using it correctly’

\citep[p.~37, AT VII:53–54]{descartes:1985_csm2}

Meditation IV

Not really convicing: does a ‘way forward’ mean a basis for knowledge?

also: doubt about clear and distinct perception

(e.g. doubt that 2+3=5)

1. It is possible to doubt things that are clearly perceived.

2. We must find justification for removing doubt.

3. Therefore, we must find justification for not doubting what is clearly perceived.

Is this a good argument. Can we reject any premises?

Matters are even clearer in the Discourse on Method ...

‘what I took just now as a rule, namely that everything we conceive very clearly and very distinctly is true, is assured only for the reasons that God is or exists

, that he is a perfect being, and that everything in us comes from him. It follows that our ideas or notions, being real things and coming from God, cannot be anything but true, in every respect in which they are clear and distinct.’

\citep[p.~130, AT VI:38]{descartes:1985_csm1}

Discourse on Method

Other passages suggest the God-first idea is wrong ...

‘I am certain that I am a thinking thing.

Do I not therefore also know what is required for my being certain about anything?

In this first item of knowledge there is simply a clear and distinct perception of what I am asserting; this would not be enough to make me certain of the truth of the matter if it could ever turn out that something which I perceived with such clarity and distinctness was false.’

‘I now seem to be able to lay it down as a general rule that

whatever I perceive clearly and distinctly is true’

Meditation III

God exists therefore clear perceptions are true

Clear perceptions are true therefore God exists?

Recall a key passage suggesting the God-first idea ...

‘I think I can see a way forward to the knowledge of other things ... since God does not wish to deceive me, he surely did not give me the kind of faculty which would ever enable me to go wrong while using it correctly’

\citep[p.~37, AT VII:53–54]{descartes:1985_csm2}

Meditation IV

‘there arises in me a clear and distinct idea of a being who is independent and complete, that is, an idea of God.

And from the mere fact that there is such an idea within me [...] I clearly infer that God also exists [...]

So clear is this conclusion that I am confident that the human intellect cannot know anything that is more evident or more certain.’

Meditation VI

I think Descartes’ strategy might be this ...

1. If we can know anything, then we can know God exists.

2. We can know something.

3. Therefore, we can know God exists.

4. But God doesn’t deceive us.

5. Therefore what we clearly perceive is true.

On my interpretation, Descartes is not offering an anti-sceptical argument.

Steve’s rough idea: \begin{enumerate} \item If we can know anything, then we can know God exists. \item We can know something. \item Therefore, we can know God exists. \item But God doesn’t deceive us. \item Therefore what we clearly perceive is true. \end{enumerate} Compare \citet{murdoch:1999_cartesian}: ‘not only is the doubt-insinuating thought not a reason for Descartes to doubt his entitlement to infer that God exists, but also he has no other reason to doubt this.’ Conflicting interpretations include \citet{rocca:2005_descartes,broughton:2003_descartes,doney:1955_cartesian}.

On my interpretation, there’s also no reason for Descartes to be offering a sceptical argument.

Two Interpretations

1. The sciences need a metaphysical foundation.

2. This foundation must include a refutation of scepticism.

‘I had seen many ancient writings by the Academics and Sceptics on this subject, and was reluctant to reheat and serve this precooked material’

Second Replies

If Descartes were refuting scepticism, the Cartesian Circle would be inescapable.

But it isn’t.

So Descartes isn’t refuting scepticism.

... or?

This passage appears to refute my position.

Actually it’s doubly bad for me (a) knowledge depends on God, and (b) it’s not knowledge if it can be doubted.

’an atheist can be clearly aware that the three angles of a triangle are equal to two right angles [...]. But I maintain that this awareness of his is not true knowledge, since no act of awareness that can be rendered doubtful seems fit to be called knowledge’

\citep[p.~101, AT VII: 141]{descartes:1985_csm2}

Second Replies

Also note what Descartes himself said ...

‘as to the fact that I was not guilty of circularity when I said that the only reason we have for being sure that what we clearly and distinctly perceive is true is the fact that God exists, but that we are sure that God exists only because we perceive this clearly: [...] I made a distinction between what we in fact perceive clearly and what we remember having perceived clearly on a previous occasion. To begin with, we are sure that God exists because we attend to the arguments which prove this; but subsequently it is enough for us to remember that we perceived something clearly in order for us to be certain that it is true. This would not be sufficient if we did not know that God exists and is not a deceiver’ \citep[p.~171, AT VII:245--6]{descartes:1985_csm2}

A Puzzle about the Senses

\section{A Puzzle about the Senses}

‘I have been in the habit of misusing the order of nature. For‘the proper purpose of [...] sensory perceptions [...] is simply to inform the mind of what is beneficial or harmful [...];
and to this extent they are sufficiently clear and distinct.
But I misuse them by treating them as reliable touchstones for immediate judgements about the essential nature of the bodies located outside us;
yet this is an area where they provide only very obscure information.’

\citep[pp.~57-8]{descartes:1985_csm2}

Descartes, Meditation IV

Sensations can have valence without representing anything

Sensory perceptions of tastes, smells, sounds, heat, cold, light, colors and the like ‘do not represent anything located outside our thought’

These sensory perceptions ‘vary according to the different movements which pass from all parts of our body to the ... brain’

Principles

(\citealp[p.~ 219, AT VIII:35]{descartes:1985_csm1} cited by \citealp[p.~348]{simmons:1999_are})

Sensations vs representations

‘Something which I thought I was seeing with my eyes is in fact grasped solely by the faculty of judgement which is in my mind’

(Meditation 2).

Is Descartes’ consistent?

Simmons shows us that Descartes is not super consistent ...

Sensory perceptions of tastes, smells, sounds, heat, cold, light, colors and the like ‘do not represent anything located outside our thought’

Principles

‘the proper purpose of [...] sensory perceptions [...] is simply to inform the mind of what is beneficial or harmful’

How can you inform if you do not represent? By being aversive or pleasurable.

Inconsistent tetrad:

1. Sensory perceptions represent things.

2. What can represent can misrepresent.

3. Anything that can misrepresent can be a source of error.

4. Sensory perceptions cannot be a source of error.

Could both claims be true?

Further evidence of the contradiction

External bodies
‘may not exist in a way that
exactly corresponds with my sensory grasp of them,

for in many cases the
grasp of the senses
is very obscure and confused.

Mere sensations could not grasp.

But at least they possess all the properties which I clearly and distinctly understand,

that is all those which, viewed in general terms, are comprised within the subject matter of pure mathematics.’

Further & further evidence of the contradiction

‘We should note here that the intellect can never be deceived by any experience, provided that when the object is presented to it, it intuits it in a fashion exactly corresponding to the way in which it possesses the object, either within itself or in the imagination. Furthermore, it must not judge that the imagination faithfully represents the objects of the senses, or that the senses take on the true shapes of things, or in short that external things always are just as they appear to be. In all such cases we are liable to go wrong, as we do for example when we take as gospel truth a story which someone has told us; or as someone who has jaundice does when, owing to the yellow tinge of his eyes, he thinks everything is coloured yellow; or again, as we do when our imagination is impaired (as it is in depression) and we think that its disordered images represent real things. But the understanding of the wise man will not be deceived in such cases: while he will judge that whatever comes to him from his imagination really is depicted in it, he will never assert that it passes, complete and unaltered, from the external world to his senses, and from his senses to the corporeal imagination’ (Rules for the Direction of the Mind, Rule 12) \citep[p.~47, AT X:423]{descartes:1985_csm1}.

‘the intellect can never be deceived by any experience, provided that when the object is presented to it, it intuits it in a fashion exactly corresponding to the way in which it possesses the object, either within itself or in the imagination.

‘[the intellect] must not judge that external things always are just as they appear to be.’

In all such cases we are liable to go wrong, as we do for example when we take as gospel truth a story which someone has told us;

‘... the the wise man will not judge that whatever comes to him from his imagination ... passes, complete and unaltered, from the external world to his senses, and from his senses to the corporeal imagination’

Rules for the Direction of the Mind, Rule 12

1. On Descartes’ view, do the senses represent things?

2. If so, how is it that the senses never misrepresent things? (Or, if they do sometimes misrepresent, why are they not a source of error)?

3. If not, why must we ‘not judge that external things always are just as they appear to be’?

\emph{Dilemma} On Descartes’ view, do the senses represent things? If so, how is it that the senses never misrepresent things? (Or, if they do sometimes misrepresent, why are they not a source of error)? If not, why must we ‘not judge that external things always are just as they appear to be’?

A resolution?

The optics suggests another idea ...

‘consider the reasons why [vision] sometimes deceives us. First, it is the soul which sees, and not the eye; and it does not see directly, but only by means of the brain. That is why madmen and those who are asleep often see, or think they see, various objects which are nevertheless not before their eyes: namely, certain vapours disturb their brain and arrange those of its parts normally engaged in vision exactly as they would be if these objects were present. Then, because the impressions which come from outside pass to the 'common' sense by way of the nerves, if the position of these nerves is changed by any unusual cause, this may make us see objects in places other than where they are ... Again, because we normally judge that the impressions which stimulate our sight come from places towards which we have to look in order to sense them, we may easily be deceived when they happen to come from elsewhere. Thus, those whose eyes are affected by jaundice, or who are looking through yellow glass or shut up in a room where no light enters except through such glass, attribute this colour to all the bodies they look at. And the person inside the dark room which I described earlier attributes to the white body the colours of the objects outside because he directs his sight solely upon that body. And if our eyes see objects through lenses and in mirrors, they judge them to be at points where they are not and to be smaller or larger than they are, or inverted as well as smaller (namely, when they are somewhat distant from the eyes). This occurs because the lenses and mirrors deflect the rays’ (Optics) \citep[pp.~172--3, AT VI:141--2]{descartes:1985_csm1}.

‘consider the reasons why [vision] sometimes deceives us.

‘those ... who are looking through yellow glass ... attribute this colour to all the bodies they look at’

Optics

Sensory perceptions of tastes,smells, sounds, heat, cold, light, colors and the like ‘do not represent anything located outside our thought’

Principles

(\citealp[p.~ 219, AT VIII:35]{descartes:1985_csm1} cited by \citealp[p.~348]{simmons:1999_are})

They do represent. But what they represent is somehow internal to the mind. Maybe what they represent is that the mind has been excited by an external stimulus of some kind.

Maybe this is what Descartes has in mind, and why he appears to go backwards and forwards on the issue of representation.

But this interpretation has two problems. First, it is implausible (because of the scientific discoveries mentioned earlier). Second, where there is representation, even of things within the mind, there is surely the possibility of misrepresentation.

Regardless of whether Descartes has a consistent, or even defensible, view on sensory perception, he is responsible for two big insights ....

Descartes’ big insights

1. The intellect is independent of sensory perceptions: it does not have to accept the principles implicit in perceptual processes.

2. We can explain why perceptual processes implicitly rely on principles which sometimes yield misrepresentations by appeal to the proper purpose of sensory perception.

Conclusion

\section{Conclusion}

Why doubt?

My Descartes is not interested in refuting the sceptic; his focus is the scientific revoltion. Doubt is an alternative to the more direct approach taken in The World.

... to refute scepticism?

image: heisenberg, founder of quantum mechanics.

(a) you cannot refute scepticism,

and (b) scepticism is correct in this sense: the world is almost certainly quite different from how you think it is.

Doubt is necessary to establish ‘anything at all in the sciences that is stable and likely to last’

But refuting scepticism isn’t going to help establish anything in the sciences.

Why is doubt necessary? To lead us away from the senses!

‘although I feel heat when I go near a fire and feel pain when I go too near, there is no convincing argument for supposing that there is something in the fire which resembles the heat, any more than for supposing that there is something which resembles the pain.

There is simply reason to suppose that there is something in the fire, whatever it may eventually turn out to be, which produces in us the feelings of heat or pain’

\citep[p.~58, AT VII:83]{descartes:1985_csm2}

Meditation VI
Treatise on Man figure 1

Treatise on Man, figure 2

Why doubt?

Not to refute scepticism.

But because doubt is ‘the easiest route by which the mind may be led away from the senses’.

Note also that Descartes is quite dismissive of doubt by the end of the Meditations (earlier said could not distinguish dreaming from waking)

‘... the principal reason for doubt, namely my inability to distinguish between being asleep and being awake. For I now notice that there is a vast difference between the two, in that dreams are never linked by memory with all the other actions of life as waking experiences are.’

If, while I am awake, anyone were suddenly to appear to me and then disappear immediately, as happens in sleep, so that I could not see where he had come from or where he had gone to, it would not be unreasonable for me to judge that he was a ghost, or a vision created in my brain, rather than a real man. But when I distinctly see where things come from and where and when they come to me, and when I can connect my perceptions of them with the whole of the rest of my life without a break, then I am quite certain that when I encounter these things I am not asleep but awake. And I ought not to have even the slightest doubt of their reality if, after calling upon all the senses as well as my memory and my intellect in order to check them, I receive no conflicting reports from any of these sources. For from the fact that God is not a deceiver it follows that in cases like these I am completely free from error.’

\citep[p.~61--2, AT VII:89--90]{descartes:1985_csm2}

Meditation VI

... or?

‘I wanted to show the firmness of the truths which I propound later on, in the light of the fact that they cannot be shaken by these metaphysical doubts. ...

I could not have left them out, any more than a medical writer can leave out the description of a disease when he wants to explain how it can be cured.’

\citep[p.~121, AT VII:172]{descartes:1985_csm2}

Third Replies

conclusion

In conclusion, ...

Why doubt?

Even at the end,
the reasons Descartes gives for doubting
remain a mystery.

(Enlighten me!)

Keyboard Shortcuts?

Lecture 10:

Descartes

[email protected]

Is there a Cartesian Circle?

A Puzzle about the Senses

Conclusion

Keyboard Shortcuts`?`