Born 12 March 1685, George Berkeley is the sort of philosopher who gives philosophy a bad name. When you first read his work you think it’s ludicrous. And you’re right, it is. Berkeley’s philosophy denies the existence of matter. According to him, there is no material world.
Modern philosophy had been started in the seventeenth century by the French philosopher René Descartes, who maintained that our only true knowledge of the world is based upon reason. Less than half a century later this Cartesianism, as it was called, was opposed by the English philosopher John Locke, who founded empiricism. Locke took a more common sense view, claiming that our only true knowledge of the world must be based upon experience.
Knowledge through experience
It was perhaps inevitable that philosophy wouldn’t remain constricted within the straightjacket of common sense for long. Just twenty years after Locke’s Essay on Human Understanding came Berkeley’s Essay Towards a New Theory of Vision, which set philosophy free from what most of us regard as reality. This carried Locke’s empirical thought through to some very non-commonsensical conclusions. According to Berkeley, if our knowledge is based entirely upon experience, we can only know our own experience. We don’t in fact know the world, just our particular perceptions of it. So what happens to the world when we are not experiencing it? As far as we are concerned, it simply ceases to exist.
So according to George Berkeley, when you don’t see something it isn’t there. This position is adopted by infants who screw their eyes closed when they wish to avoid eating any more spinach and prune puree. Yet by the time we have achieved the exalted status when we eat our spinach and prunes separately (or not at all), we have usually grown out of this attitude. But not Berkeley. According to him, a tree isn’t there if we don’t see it or perceive it in any other way, such as touch or smell. So what happens to the tree? Berkeley was a God-fearing man, who eventually became a bishop. This led him to an ingenious explanation as to how the world persists when we don’t experience it.
In other words: we can know that the world exists only when we are perceiving it. Yet even when we are not directly perceiving the world, it is nonetheless supported by the continuous perception of an all-seeing God.
George Berkeley’s empirical conclusion (no permanent reality) and his miraculous solution (an ever-present God) sounds like so much sophistry. Today’s sensibilities for the most part have little time for such apparent intellectual trickery – which seems to belong more to the Middle Ages than to our age of science. So it comes as some surprise when we find that subatomic physics has been forced to a surprisingly similar conclusion to Berkeley’s.
According to Heisenberg’s uncertainty principle, we cannot simultaneously measure both the momentum and position of a subatomic particle. If one of these elements is measured (i.e., perceived), the other remains indeterminate. Thus, in a very real sense, only the quality which is being perceived (the measured position, say) is real, and the other quality (its momentum: mass and velocity) does not exist in any determinable form. We can only ‘know’ the one we are perceiving. The other element is in a sense ‘there’ (as if perceived by an all-seeing God), but it cannot come into any determinate existence until we perceive it.
George Berkeley’s philosophy appeared to take empiricism to a ludicrous extreme. But when we follow through the implications of our common sense assumptions to their logical conclusions, the result often has little to do with the ‘obvious’ common sense assumptions from which we started. Common sense is how we attempt to run our everyday lives. But if we wish to progress beyond the imprecision and muddle of everyday existence to some more certain truth, we frequently have to abandon the obvious. As Einstein remarked: ‘Common sense is the collection of prejudices acquired by age eighteen.’