Berkeley and the mind-dependence of reality (30-Oct-2003)

Descartes and Locke seem to share the view that while matter does have extension, the other qualities (e.g. colour) which we perceive in a material object are in some way secondary, and should not be regarded as actually existing in the object. One is tempted to ask why there should be such a division, and why should we imagine that, as Locke says, "the ideas of primary qualities of bodies, are resemblances of them, and their patterns do really exist in the bodies themselves".

Berkeley seems to take this thought to an extreme conclusion by suggesting that none of the qualities which we perceive is related to any property that exists in material substance - in fact there is no such thing as material substance; rather we experience a set of sensations which give rise to ideas in us, and these ideas leads us to suppose that a given object exists. An object that we perceive only exists insofar as we are perceiving it. It therefore follows that if no-one is perceiving it, then it does not exist at all.

On first reading, Berkeley's position seems to me quite beguiling, but also frustrating, because there doesn't appear to be any way that we can assess whether it is true (it fails A.J. Ayer's "criterion of verifiability"). Since, according to Berkeley, we can only perceive objects when they are being perceived, then by definition we can never know whether they continue to exist when we are no longer perceiving them. Additionally, it is hard not to respond "so what?": idealism may be an attractive way to explain the world, but what benefit does it do us to understand it?

But today, quantum physics tells us that material objects do appear to be affected by our observation of them, in a way that seems as counter-intuitive as Berkeley's suggestion. Perhaps, in the same way that Democritus postulated a universe made up from indivisible particles many years before scientists had the inclination or ability to search for those particles, Berkeley's ideas have some relevance to our understanding of how the world works.