To: Graham H.
From: Geoffrey Klempner
Subject: The idealism of Bishop Berkeley
Date: 5th August 2011 13:46

Dear Graham,

Thank you for your email of 24 July, with your fourth essay for the Possible World Machine, in response to the question, ''To exist is either to perceive or to be perceived.'; How would you explain Bishop Berkeley's idealism to someone who knew nothing about philosophy?'

This is a very nice exposition of Berkeley's theory, which focuses on Berkeley's motivation for adopting an idealist solution to the problem of perception as well as giving a brief account of his argument.

The motivation was, as you say, to combat scepticism. Not only is Berkeley concerned with the threat of scepticism posed by Locke's 'veil of perception' theory, but also sees the weak link in Descartes mind-body dualism.

This could also be described as a 'sceptical challenge', namely to identify the 'locus of interaction'.

How do we know that our thoughts cause actions, or that physical events in the outside world cause us to have perceptions? How can mind act on matter? The problem is acute for Descartes, precisely because he rejects the popular notion of mental substance as some kind of ghostly ectoplasm, table tapping ghosts etc. Mind has none of the attributes of body. It is not located, as body is. Descartes offers as a hypothesis that the interaction takes place in the pineal gland, in the brain. (We now know that the pineal gland has an altogether different function.) The point is, though, that any hypothesis will do, because any hypothesis is equally empty. Cartesian physics neatly avoids the problem posed by the conservation of energy as 'matter' is defined purely in geometric terms, so that 'movement' (momentum) rather than energy is conserved. But the explanatory gap remains.

The problem of interaction, as the problem of scepticism, were familiar topics of debate in Berkeley's time. In one fell swoop he solved both problems. Or did he?

As you don't say much about Berkeley's 'master argument', I won't either. Let's concentrate instead on the question of how good an explanation Berkeley offers, as an alternative to dualism.

What is matter? (Don't say, 'never mind'!). As you note, it is a notion with a long history going back to the Presocratics. But the Presocratics didn't have much to say about consciousness. (According to the atomists, as Aristotle noted, the atoms which compose the soul are very 'slippery' so they get everywhere, they enable a body to 'move' itself.) Descartes, in his sceptical mood, wonders whether 'matter' exists or not. But what difference would it make, exactly? An evil demon is a creator of an 'unreal' virtual reality world which we took to be real. A benevolent deity is a creator of a 'real' world. But Descartes also argues that a material object, no less than an immaterial substance such as a soul, only 'exists' for as long as God exercises his continual creative force. This isn't 'matter' as the atomists knew it, stuff that remains no matter what, and is incapable in principle of being destroyed. This table and this computer would blink out of existence in a moment if God relaxed his vigilance.

It doesn't take a genius to conclude that 'stuff' which only 'exists' for as long as God is making it exist, whose sole purpose is to 'explain' perception, can be taken out of the equation without loss. In Berkeley's theory, the 'object' exists as an 'archetype' in God's mind, of which our perceptions are 'ectypes'. Replace these words by 'matter' and 'perceptions' and the sense remains virtually the same.

It was Kant who saw the major weakness in Berkeley's position. Actually, two weaknesses, although arguably Berkeley could have happily accepted the first point:

1. In his 'Refutation of Idealism' (in the 2nd edition of 'Critique of Pure Reason') Kant argues that perception is only possible if experience takes the form of objects arranged in space. Not every sequence of mental events is a 'possible experience', only those which can be interpreted by a theory - the theory of an external world, and perceivers who occupy spatial positions in that world.

2. A criticism which Kant levelled at Leibniz, although arguably this applies equally to Berkeley, is that talk of God's 'experience' or the things in God's 'mind' is an illicit extension of a conception which applies only within the world of phenomena, the world of *our* experience. We are not in a position to say anything about how things are 'in reality' ('in God's mind'). Kant concluded that 'things in themselves' or 'noumena' are unknowable. Berkeley, in claiming to describe these 'things' is just talking nonsense.

Kant called his theory 'transcendental idealism'. His 'refutation of idealism' was a response to critics of the 1st edition of 'Critique of Pure Reason' who complained that his theory was merely a version of Berkeleian idealism. But the critics were at least partly right. Transcendental idealism (the theory of phenomena and noumena) is still idealism. 'Matter' is merely a concept we apply to experience, like 'hot' or 'red'.

Disproving that theory is (still) one of the great challenges of metaphysics.

All the best,

Geoffrey