Story of Psychology - Morton Hunt [51]
The thesis is sound, and a genuine contribution to perception theory. Moreover, his breaking down the seemingly simple experience of depth perception into more basic experiences anticipated or perhaps even led to the “molecular” approach of later psychology—the effort to analyze all experiences into their simplest components.
But if Berkeley was realistic in his psychology of perception, he was unworldly in the philosophic theory for which he is famous. Philosophy had long created problems for psychologists; Berkeley’s psychology created a problem that would stump philosophers. It started when, as a youth of twenty-one, he decided that materialistic Newtonian science was endangering religion; he told himself in a diary that if he could only do away with the doctrine of matter, the “monstrous schemes” of “every wretched sect of atheists” would collapse.41
For a twenty-one-year-old to dream of doing away with the worldwide belief that matter exists—and to publish a book at twenty-five, The Principles of Human Knowledge (1710), expounding that dream—sounds ludicrous, if not insane. (His third important work, published in 1713, was a dialogue restating the argument.) But Berkeley was simply following through to its ultimate conclusion Locke’s distinction between primary and secondary qualities. If all knowledge comes from our perceptions, we know nothing of the external world except them; but they are only secondary qualities. How do we know that the matter or substance in which primary qualities are said to reside really exists? In dreams, we see trees, houses, mountains vividly, but they are only illusions; why should we suppose our waking perceptions are better evidence that anything real exists? In Berkeley’s words:
But though it were possible that solid, figured, movable substances may exist without the mind, corresponding to the ideas we have of bodies, yet how is it possible for us to know this? Either we must know it by sense or by reason. As for our senses, by them we have only the knowledge of our sensations… [As for reason,] what reason can induce us to believe the existence of bodies without the mind from what we perceive? … It is possible we might be affected with all the ideas we have now, though there were no bodies existing without, resembling them. 42
What exists, as far as we can know, is only what we perceive. Esse est percipi: to be perceived is to be. What is not perceived may as well not exist, for all the difference it makes to us (a doctrine that will reappear in modern times as phenomenological psychology, an offbeat by-product of existentialism).
Berkeley was no fool; he acknowledged in the Preface to his Principles that some passages in it, taken by themselves, might seem to have “absurd consequences.” And scoffers have accused him of claiming that there is no real world whatever and that all existence is only in our imagination—that a tree exists when we see it but ceases to when we look away. Berkeley, however, rescued the universe by recourse to God, the Permanent Perceiver, Who sees all things all the time. There may be no material world, but the universe of His perceptions is steady and enduring; even when we do not see a thing, He does, and it therefore does not cease to exist when we cease looking at it. The twentieth-century British theologian Father Ronald Knox admirably summed up Berkeley’s view in a famous limerick:
There was a young man who said “God
Must think it exceedingly odd
If he finds that this tree
Continues to be
When there’s no one about in the Quad.”*
Berkeley’s theory