To: David F.
From: Geoffrey Klempner
Subject: Hume on personal identity
Date: 24 August 2005 10:19

Dear David,

Thank you for your email of 15 August, with your first essay for the Possible World Machine, and for your 2 emails of 22 August with further comments.

Hume's remark ('For my part, when I enter most intimately into what I call myself, I always stumble on some particular perception or other...') occurs in the part of the Treatise dealing with 'Sceptical and Other Systems of Philosophy' (section VI. 'Of Personal Identity'), where he also argues that - from a philosophical point of view - no meaning can be attached to the notion of the 'distinct and continued existence of objects'.

Hume begins the section on personal identity by noting, 'There are some philosophers, who imagine we are every moment intimately conscious of what we call our SELF; that we feel its existence and its continuance in existence...'.

This is important, because it helps locate the dialectical context of Hume's remark.

In the earlier section II, 'Of Scepticism With Regard to the Senses' the scepticism in question is scepticism concerning the very meaning of the claim that objects 'continue' to exist when not perceived and 'distinct' from the act of perception. It's not simply that we don't know or can't prove this. And similarly, with the soul, the question is not simply, 'Here we have this idea of a soul, now, can we prove that souls exist or not?' but rather, 'What are these philosophers are talking about? - I haven't the faintest idea!' So it would not be correct to say, as you do, that 'Hume is not arguing against the existence of the soul'.

Of course, Hume is being disingenuous. He does know. Just as (when he goes off to play a game of backgammon) he knows what spatio-temporal objects are. In his official philosophy these are 'fictions', psychological constructs, not concepts that can be justified by reason or logic. We psychologically can't help attributing our thoughts, feelings and sensations to a 'self' which 'has' them, but if we just look at the plain facts of experience - instead of the mental pictures that we are tempted to construct - there's nothing there to see.

A much better candidate for agnosticism about the soul would be Locke. In his treatment of personal identity, Locke proposes a 'soul swap' thought experiment. During the night the souls of a prince and a pauper are exchanged, while their memories remain unaffected. So the prince still thinks he is a prince, the pauper still thinks he is a pauper. What this shows is that the soul hypothesis is otiose. Whereas according to Hume it is meaningless.

You are right to point out that Hume is not arguing against a dualist view of the mental. It might seem that a materialist would be saved from the 'bizarre implications' because you can simply identify the self with something we don't see when we look inside ourselves, namely our own brain. With his 'sceptical' view of the nature of physical objects, that option is not open to Hume.

What about the bizarre idea that 'I' do not exist while asleep? Hume has a logical answer to the question of the definition of 'I' which is astoundingly simple. All the 'ideas' and 'impressions' in the universe are neatly partitioned into sets which are *present* to one another at a given time. No two sets overlap. You and I can have similar feelings but as a matter of logic we can't share numerically the same feeling - not even if we were telepathic. My sense of identity over time is simply a product of continuity between the present set of co-present ideas and impressions and my memories ('ideas') of previous co-present sets. In this logical sense, I do 'exist' while asleep.

Hume's great contribution to philosophy - as he saw it - was his 'science of human nature', or, as we would call it, psychology. He would have been enthusiastically in favour of research on the concept formation of infants (cf your note 3). Concepts are formed through the association of ideas, concepts which when examined by the philosopher, i.e. logically, prove to be mere 'fictions'. All the treatises that have been written about the soul, god or the ultimate destiny of man are fit only for committing to the flames.

Further thoughts

'Consciousness'. Hume lumps thoughts, feelings, sensations and concepts all under the heading of 'impressions and ideas'. That is the given. It is in relation to this given that sceptical questions (concerning 'external' objects, or a 'self') are raised. It would be nonsensical for Hume to question whether ideas and impressions exist. (I don't believe he ever refers to the notion of 'consciousness'.)

There are lots of 'dualisms'. Cartesian interactionism, Spinozist dual-aspect theory, epiphenomenalism, parallelism...

- Then there's my so-called 'theory', the dualism of subjective and objective worlds.

There are still some defenders of idealism (your preferred solution to the mind-body problem). Foster, in 'The Case for Idealism' in one of his arguments uses Cartesian idea that 'things would be for me just as they are now if material objects don't exist'. If that is true, then, as Berkeley argued, matter is simply redundant.

Nothing you say here reminds me of anything that Strawson has written. There is a short piece by Strawson, 'Self, Mind and Body' which very entertainingly pokes holes through the Cartesian notion of a soul. Strawson claims that since there are no criteria of identity for souls, there is no logical difference between my having one soul or a thousand souls. This is similar to Kant's argument in the 'Paralogisms of transcendental psychology' (from Part II of Critique of Pure Reason) that there would be no difference between having one soul or a sequence of souls each communicating its states to the next like a line of colliding billiard balls.

On earthworms. Suppose Hitler's brain was preserved by an evil scientist, and a section was mashed up and injected into your skull. You wake up thinking you are Hitler. Under what circumstances would it be true to say that, as a result of this operation, you are Hitler? Or, what if this was done to a dozen people? would there be a dozen Hitlers?

There's more discussion of these kinds of thought experiment in the unit on personal identity.

All the best,

Geoffrey