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\title {Descartes \\ Lecture 07}
 
\maketitle
 

Lecture 07:

Descartes

\def \ititle {Lecture 07}
\def \isubtitle {Descartes}
\begin{center}
{\Large
\textbf{\ititle}: \isubtitle
}
 
\iemail %
\end{center}
 
\section{The Senses and Appearances}
 
\section{The Senses and Appearances}

does not represent anything

a bruise

a meteor crater

an antique gold coin

an electric shock

does represent something

a tatoo of your Mum

an inscription

a treasure map

a thought about electricity

Do sensory perceptions represent 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).

What about appearances?
(Partially immersed stick appearing bent, e.g.)

How can things appear to be other than they are?

-- Sensory perceptions can misrepresent them.

\subsection{Descartes’ Three Grades of Sensory Response} ‘when I see a stick, it should not be supposed that certain ‘intentional forms’ fly off the stick towards the eye, but simply that rays of light are reflected off the stick and set up certain movements in the optic nerve and, via the optic nerve, in the brain, as I have explained at some length in the Optics. This movement in the brain, which is common to us and the brutes, is the \textbf{first grade of sensory response}. This leads to \textbf{the second grade}, which extends to the mere perception of the colour and light reflected from the stick; it arises from the fact that the mind is so intimately conjoined with the body that it is affected by the movements which occur in it. \emph{Nothing more than this should be referred to the sensory faculty, if we wish to distinguish it carefully from the intellect.} But suppose that, as a result of being affected by this sensation of colour, I judge that a stick, located outside me, is coloured; and suppose that on the basis of the extension of the colour and its boundaries together with its position in relation to the parts of the brain, I make a rational calculation about the size, shape and distance of the stick: although such reasoning is commonly assigned to the senses (which is why I have here referred it to \textbf{the third grade of sensory response}), it is clear that it depends solely on the intellect’ \citep[p.~295, AT VII:437]{descartes:1985_csm2}.

‘when I see a stick, it [is] simply that rays of light are reflected off the stick and set up certain movements in the optic nerve and, via the optic nerve, in the brain

This movement in the brain ... is the first grade of sensory response.

the second grade ... extends to the mere perception of the colour and light reflected from the stick [...]

Nothing more than this should be referred to the sensory faculty, if we wish to distinguish it carefully from the intellect.

But suppose that ... I make a rational calculation about the ... shape ... of the stick:

although such reasoning is commonly assigned to the senses (which is why I have here referred it to the third grade of sensory response), it ... depends solely on the intellect.

Sixth Replies

What about appearances?
(Partially immersed stick appearing bent, e.g.)

How can things appear to be other than they are?

-- Sensory perceptions can misrepresent them.

-- They cannot. There are no incorrect appearances.

The only appearances are colour and light. Any representation of the stick’s shape ‘depends solely on the intellect’.

Does reflection on appearances show that sensory perceptions must represent things outside our thought?

What is Descartes claiming about perceptual appearances in that passage about the stick? (That there aren’t any.)

philosophical
methods

informal observation,

guesswork (‘intuition’),

reasoning,

& theoretical elegance

First, think about the methods philosophers use. Am I missing any?
Next, think about how philosophers construct theories of perception ...
Descartes clearly thought that understanding perception was a matter for science. (See also his Optics!)

‘any given movement occurring in the part of the brain that immediately affects the mind produces just one sensation in it;

\citep[p.~60, AT VII:87]{descartes:1985_csm2}

Sixth Meditation

Does reflection on appearances show that sensory perceptions represent things outside our thought?

If so, is Descartes wrong about error?

What did Descartes say about error? Let me remind you ...

The intellect is the faculty of representation.

The will is what affirms or denies something represented

Judgement occurs when the intellect represents something which the will affirms (or denies).

Error occurs when the will affirms (or deines) incorrectly.

a complication

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

Rules for the Direction of the Mind, Rule 12

 

Refuted by Science?

 
\section{Refuted by Science?}
 
\section{Refuted by Science?}

Mitroff, Scholl and Wynn 2005, figure 2

Compare Scholl and Mitroff’s bouncing/streaming study. This study: (i) suggests solidity may be a constraint, at least sometimes; (ii) indicates that phenomenology and object indexes may not perfectly align
Mitroff et al p. 74: ‘we induced a strong bias to consciously perceive streaming, by using smooth, constant, and reasonably fast motion. This allows us to provide the clearest possible situation in which to evaluate the relationship between conscious percepts and object files.’ expectations can come apart in some situations.

Mitroff, Scholl and Wynn 2005, figure 3

[video]

Mitroff, Scholl and Wynn 2005

Mitroff, Scholl and Wynn 2005

Descartes: The will is the sole source of error.

Steve: What about sensory perceptions?

Descartes: Sensory perceptions do not represent.*

Steve: That’s untrue because sensory perceptions can conflict with judgements.

also representational momentum ...

You can do RM with the spiral setup too ...

Freyd & Jones, 1994 figure 2

predicted memory shifts: the representational momentum effect you would get if your subjects’ representational momentum were predicting the straight path.

Yet ‘our subjects had relatively accurate conscious knowledge of the trajectory of a ball exiting a spiral tube (63% to 83% chose the correct path; only 4% chose the spiral path).’

\citep[p.~975]{freyd:1994_representational}
it really is perception!

‘subjects showed a memory shift for a path that the majority of subjects did not consciously consider correct’

\citep[p.~975]{freyd:1994_representational}

Descartes: The will is the sole source of error.

Steve: What about sensory perceptions?

Descartes: Sensory perceptions do not represent.*

Steve: That’s untrue because sensory perceptions can conflict with judgements.

Or?

Always consider objections to your views!
Which claim should we reject?

Descartes: The will is the sole source of error.

Steve: What about sensory perceptions?

Descartes: Sensory perceptions do not represent.*

Steve: That’s untrue because sensory perceptions can conflict with judgements.

conclusion

In conclusion, ...
  • The intellect is the sole source of error
  • Thf. the senses do not represent
  • Thf. there are no perceptual appearances ... and no representational momentum
  • So if there are perceptual appearances, Descartes’ view of error collapses.

Part 2