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\title {Descartes \\ Lecture 01}

\maketitle

Lecture 01:

Descartes

[email protected]

\def \ititle {Lecture 01}

\def \isubtitle {Descartes}

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\textbf{\ititle}: \isubtitle

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\emph{Overall Topic}: What, according to Descartes, is the relation between a sensory perception and the thing perceived?

\emph{Question for this Lecture}: How can we acquire knowledge about the essential nature of the bodies located outside us?

\emph{Argument of this Lecture}: \begin{enumerate} \item Sensory perceptions provide only very obscure information about the essential nature of bodies. \item Therefore, we cannot acquire knowledge about the essential nature of the bodies located outside us through sensory perceptions alone. \end{enumerate}

\section{Exercise} The diagram shows a thin curved metal tube. Imagine you are looking down the tube. A metal ball is put into the end of the tube indicated by the arrow. The ball is then shot out of the other end of the tube at high speed. Please draw the past the ball will follow after it comes out of the tube \citep{mccloskey:1980_curvilinear}.

McCloskey et al, 1980 figure 1 (part)

[Start with folk physics error (trajectories) Later: Also use Freyd representational momentum: it is based on sensroy erros!]

\section{A Question}

The picture Descartes opposes on two counts: (i) extension is the single essence of all external bodies, and (ii) we do not know essence through sensory perception.

How can we acquire knowledge about the essential nature of the bodies located outside us?

Each body has a form, which is its essential nature.

What is that?

\section{Forms} What is an Aristotelian form? It ‘is not a subset of the properties that the organism [or thing] has, but rather a set of those that are proper to it, and towards which it strives or tends. Why does an acorn develop into an oak rather than a pig? Because of its special relation to the form that defines oak: it develops as it does because, while still an acorn, it lacks some of the properties that oaks have, and is somehow drawn towards instantiating that form more fully’ \citep[p.~10]{bennett:2003_learning}.

It’s cat form is what makes a cat catty, and what makes the kitten grow into a cat (when things go well).

When a body is perceived, its form thereby enters the mind.

No, be serious. How could a form enter the mind? When you perceive a cat, it’s not that the cat gets inside your mind. (Sounds painful.) So how could the form enter your mind?

It’s that cat distracting us. Let’s get serious.

When a body is perceived, your sensory perception resembles the body’s form.

Thanks to this resemblance, your sensory perception acquaints you with the forms (essential natures) of bodies.

This is based on: ‘According to the scholastic theory, the forms that entered the senses and thereafter the mind from external objects made the contents of the senses and the mind like the external objects: the objects, the senses, and the mind were supposed to have in them the very same forms’ (Sorell 2001 p. 75).

not
Descartes’ view

In fact Descartes wanted to oppose this view. Why did he want to oppose it? And how Descartes oppose it?

\section{The Proper Purpose of Sensory Perceptions}

\section{Key Quote from \emph{Meditations}}

‘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

What is the proper purpose of sensory perceptions? (Have a guess.)

What does this mean?

What is this?

What else is unclear in this passage? (Make sure you keep notes on everything that is unclear.)

p related passage [*TODO: move to handout]

‘My nature, then, in this limited sense, does indeed teach me to avoid what induces a feeling of pain and to seek out what induces feelings of pleasure, and so on. But it does not appear to teach us to draw any conclusions from these sensory perceptions about things located outside us without waiting until the intellect has examined the matter. For knowledge of the truth about such things seems to belong to the mind alone, not to the combination of mind and body’ \citep[p.~57]{descartes:1985_csm2}.

How can we acquire knowledge about the essential nature of the bodies located outside us?

Each body has a form, which is its essential nature.

When a body is perceived, its form thereby enters the mind.

When a body is perceived, your sensory perception resembles the body’s form.

Thanks to this resemblance, your sensory perception acquaints you with the forms (essential natures) of bodies.

Which of these claim’s does Descartes claim about the proper purpose of sensory perceptions justify us in rejecting?

How can we acquire knowledge about the essential nature of the bodies located outside us?

So here’s the question, as I keep saying.

Sensory perceptions provide only very obscure information about the essential nature of bodies.

∴ Not by treating sensory perceptions as a basis for judgements about them.

So far: Descartes view that Sensory perceptions provide only very obscure information about the essential nature of bodies

We still don’t know why anyone should think that sensory perceptions provide only very obscure information. Nor do we know whether Descartes is right about this.

The Obscurity of Sensory Perceptions

\section{The Obscurity of Sensory Perceptions}

Ok, so I was saying this ...

How can we acquire knowledge about the essential nature of the bodies located outside us?

Sensory perceptions provide only very obscure information about the essential nature of bodies.

∴ Not by treating sensory perceptions as a basis for judgements about them.

How might you defend this claim? (That sensory perceptions provide only very obscure information about the essential nature of bodies.)

Recall this question

McCloskey et al, 1980 figure 1 (part)

McCloskey et al, 1980 figure 2D

\section{Impetus}

The person who sets the ball moving impresses in it a certain impetus, [which acts] in the direction toward which the mover was moving the body, either up or down, or laterally, or circularly’ (Buridan, 13xx; cited by McCloskey et al).

But what does this tell us about sensory perceptions?

People make wrong judgements. So what? What does this tell us about sensory perceptions?

\section{Perceiving Impetus}

representational momentum

Sometimes when adult humans observe a moving object that disappears, they will misremember the location of its disappearance in way that reflects its momentum; this effect is called \emph{representational momentum} \citep{freyd:1984_representational,hubbard:2010_rm}.

The trajectories implied by representational momentum reveal that the effect reflects impetus mechanics rather than Newtonian principles \citep{freyd:1994_representational,kozhevnikov:2001_impetus,hubbard:2001_representational,hubbard:2013_launching}. And these trajectories are independent of subjects' scientific knowledge \citep{freyd:1994_representational,kozhevnikov:2001_impetus}. Representational momentum therefore reflects judgement-independent expectations about objects’ movements which track momentum in accordance with a principle of impetus.% \footnote{ Note that momentum is only one of several factors which may influence mistakes about the location at which a moving object disappears \citep[p.\ 842]{hubbard:2005_representational}. %: %\begin{quote} %`The empirical evidence is clear that (1) displacement does not always correspond to predictions based on physical principles and (2) variables unrelated to physical principles (e.g., the presence of landmarks, target identity, or expectations regarding a change in target direction) can influence displacement.' % %... % %`information based on a naive understanding of physical principles or on subjective consequences of physical principles appears to be just one of many types of information that could potentially contribute to the displacement of any given target' %\end{quote} }

Hubbard 2005, figure 1a; redrawn from Freyd and Finke 1984, figure 1

Hubbard 2005, figure 1b; drawn from Freyd and Finke 1984, table 1

\textbf{Representational momentum suggests that there are automatic processes which predict the future trajectories of physical objects.}

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}

‘the representational momentum memory shift for a ball following a spiral path after exiting a tube is greater than the memory shift for a ball following the physically correct linear path. A curvilinear path, midway between the spiral and straight paths, produces shifts midway between those for the other two paths’

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

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}

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

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

Freyd & Jones, 1994 p. 975

How can we acquire knowledge about the essential nature of the bodies located outside us?

Sensory perceptions provide only very obscure information about the essential nature of bodies.

∴ Not by treating sensory perceptions as a basis for judgements about them.

This is all by way of a demonstration that Descartes was right. Sensory perceptions really do provide only very obscure information about the essential nature of bodies.

Just one small problem: how are we going to answer this question?

one last thing

Bennett mentions something Turnbull says about Aristotle's science:

Aristotelian physics ‘is reasonably effective for organizing bodies of knowledge.

From the perspective of modern physical and biological science, however, it is severely crippled by its close linkage with what Wilfrid Sellars calls ‘the manifest image’, i.e. what is available to us by means of our very limited sense organs. [...]

The tie to entities known through perception prevents access to—much less the discoveries of—modern physics (and, consequently, chemistry and biology)’

(Turnbull 1988, p. 120 cited by \citealp{bennett:2003_learning}.)

Turnbull 1988, p. 120

This is what Descartes saw, and that’s what he is trying to explain in the Meditations.

The usefulness of extensive doubt “lies in freeing us from our preconceived opinions, and providing the easiest route by which the mind may be led away from the senses.”

In studying the Mediations, we can have a lot of fun with sceptical arguments involving dreams and demons, and other bits and pieces. These have been widely examined by philosophers, most quiet critical. What you must never forget is that Descartes’ fundamental insight was correct--- Adherence to Aristotelian physics is based on the assumption that the model of the physical implicit in human sensory perception is the truest, most accurate model of the physical there is; and this assumption is incorrect.

Practicalities

\section{Practicalities}

books

Descartes’ Meditations (CUP)

Hatfield

\section{Books} Core text: \citep{descartes:1985_csm2}. Useful background (find one you like): \begin{itemize} \item Broughton, Janet 2002. Descartes' Method of Doubt. (Princeton University Press) \item Hatfield, G. 2014. Descartes’ Meditations [The Routledge Guidebook to]. London: Routledge. \item Newman, Lex "Descartes' Epistemology", The Stanford Encyclopedia of Philosophy (Winter 2016 Edition), Edward N. Zalta (ed.). \item Williams, B. 1978. Descartes: The Project of Pure Inquiry. Hassocks: Harvester Press. \item Wilson, Margaret. 1978. Descartes (Routledge). \end{itemize} \emph{Tip}: Hatfield is an invaluable reference. Any time you write about a passage from the Mediations, check what Hatfield writes about that passage.

web

seminar tasks

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assessment

The questions are on moodle.

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Lecture 01:

Descartes

[email protected]

The Obscurity of Sensory Perceptions

Practicalities

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