To: Marcus S.
From: Geoffrey Klempner
Subject: Mind-body problem and the definition of identity
Date: 26 August 2004 14:32

Dear Marcus,

Thank you for your email of 17 August, with your second essay for the Philosophy of Mind program, in response to the question, 'What is identity? What is the relevance of a definition of 'identity' to the problem of the relation between mind and body?'

What is identity? How is the concept of 'identity' logically defined? You do not give a direct answer to this question, but offer instead a pregnant metaphor: an entity has 'an irreducible space around it' which marks it off from other entities.

We can see this intuitive principle in application non-metaphorically when we look around at the world. Consider the identity of a cloud. There are days when you can literally count the number of clouds in the sky. Each fluffy white object is clearly defined against a blue background, there is no doubt where one cloud ends and another begins.

Consider two clouds in the sky. The identity of cloud A is unaffected by what happens to cloud B because of the distance that separates A and B. A can exist without B and B without A. A is not any part of B's 'being' nor is B any part of A's 'being'.

This principle of separability is what Descartes appeals to in his argument, in Meditation 6, that mind is distinct from body. The very fact that an evil demon *might* be deceiving me into thinking that there exists a world of material objects in space when there is in reality no such world demonstrates, or so Descartes believed, that the 'mental substance' which I know as 'I' or 'my consciousness' is distinct from the 'physical substance' which I know as my body.

Unlike the case of our two clouds, this is not a spatial distinctness.

The soul, as 'thinking substance', has *none* of the attributes of body. That means that my soul is not located in space. It is not 'in' me, nor is it anywhere else. (The soul is not a 'breath of wind, a vapour' Descartes says pointedly in Meditation 1.) My soul is tied to this particular body by the 'locus of interaction' (the pineal gland, as Descartes believed). What GK's soul thinks affects this particular body, and what happens to this particular body affects what GK's soul thinks. That is how bodies and souls are paired up.

In Meditations 6 Descartes says something else very important: 'My soul is not lodged in my body as a pilot in a ship.'

This seems to be exactly the point you make with your example of the Martian rover. Descartes would in fact agree with much that you say about the practical inseparability of mind and body, their intimate interconnection.

Nevertheless, Descartes thinks, soul and body are two and not one.

This is where our understanding of the concept of identity becomes crucial. In the program, two points are made about this.

In support of Descartes, it is argued that nothing could *count* as showing that body and soul are 'one' because of the impossibility of answering the question, 'One what?' Having defined the soul as an entity which appears from subjective perspective, and the body as something that appears from the objective perspective, the very possibility of identifying these two entities is logically ruled out. There is no bridge between the two perspectives, no route that you can 'travel' that takes you from one to the other.

Against Descartes, there is the argument that the soul, considered as capable in principle of existing apart from the body has no principle of self-identity. As I write these words, there could be a dozen, or a million identical 'souls' thinking the thoughts I am thinking now. Nor is there any way to define identity of a disembodied soul over time. My experience would be just as it is now if the 'mind' of GK consists of a series of momentary 'souls' each of which exists for only a second, before dying and passing on its states to the next, like a line of colliding pool balls.

I would not question the historical judgement that Cartesian dualism has had a bad legacy. For example, Descartes believed, on the basis of his metaphysics, that animals are mere machines, bodies without souls. Anyone who cares about the welfare of animals would be aghast at the idea that humans feel and animals do not.

Much of contemporary philosophy, both in the Anglo-American tradition and the continent, can be seen as an attempt to overcome the dualist legacy and resolve the mind-body split.

As I try to show in the program, much of the effort has to go towards questioning the Cartesian assumption of the inviolability of the subjective perspective, the 'incorrigibility' of my knowledge of my own mental states. As long as this assumption is allowed to stand, dualism cannot be defeated.

All the best,

Geoffrey