Berkeley's Idealist Argument from Variable Perceptions

George Berkeley (1685-1753) (pronounced as in Charles Barkley, not as in the University of California at Berkeley), Bishop of Cloyne, was an Anglo-Irish philosopher, one of the three most prominent exemplars (along with John Locke and David Hume) of the British Empiricist school of thought.

Berkeley is perhaps the most famous pure metaphysical idealist in the history of philosophy. An idealist (in the context of metaphysics or epistemology-obviously the term can mean very different things in other contexts) is one who holds that all reality is spiritual, that matter is illusory or reducible to spirit. (As opposed to a materialist, who contends that all reality consists solely of matter, or a dualist, who holds that reality contains both irreducibly material elements and irreducibly spiritual elements.)

When people are first confronted with Berkeley's idealism, they are nearly always puzzled by it. It seems so self-evidently absurd to claim that there is no material world, that people think maybe Berkeley didn't really mean that literally but was claiming something else, or maybe just that it's one of those crazy things philosophers say that shows why they shouldn't be taken seriously.

In a famous anecdote, biographer James Boswell recounts of English author Dr. Samuel Johnson, "After we came out of the church, we stood talking for some time together of Bishop Berkeley's ingenious sophistry to prove the nonexistence of matter, and that everything in the universe is merely ideal. I observed, that though we are satisfied his doctrine is not true, it is impossible to refute it. I never shall forget the alacrity with which Johnson answered, striking his foot with mighty force against a large stone, till he rebounded from it-'I refute it thus!'"

Though we may still end up finding it implausible, let's try to at least understand how and why Berkeley came to the conclusions he did (and why the good doctor's "refutation" misses the point).

Berkeley raises multiple points in support of his version of metaphysical idealism, but we'll look at just one of them in particular, what might be called "the argument from variable perceptions."

Berkeley's starting point is that we really only have direct awareness of our own ideas and mental states (which echoes an insight of René Descartes about a century earlier). Anything else, including the most "obvious" claims about the material world and even our own bodies, can at best be inferred. We reason from our mental states to alleged causes of them.

Already Berkeley has cast the material world into some doubt, and at least left it open to argument. If we don't directly perceive matter, and its very existence is a fallible causal hypothesis, then maybe other hypotheses could explain the same data as well or better.

In a sense, Berkeley is just taking things one step farther than where Locke and others had already gone. Some philosophers already had conceded that not every property we loosely attribute to an object is really a part of that object. Many are in effect added by our minds.

For example, in the absence of conscious beings with the appropriate sense organs, nothing would have an objective "taste." Being "sour," "sweet," etc., isn't a property of a physical object per se, but is added by the mind through perception.

Same with color. Color again depends on the way our sense organs and minds perceive light reflecting off an object; it's not a property of the object itself.

The evidence most commonly cited for why these properties are not really in the object itself is that perceptions of them can differ from person to person and from time to time. Temperature can be perceived differently for instance. If you put one index finger in ice water and one in hot water, and then you put them both in the same water, that water will feel warm to the one finger and cool to the other. Since the water itself can't really be simultaneously warm and cool, so the argument goes, temperature must not exist in the object independent of perception, but instead be added by the mind.

Based on these considerations, Locke had drawn a distinction between "primary" and "secondary" properties or qualities. Primary qualities are those the object really has, like size, shape and number, and secondary qualities are those that are added by the mind through the process of perception, like color, taste, and smell.

So the theory is, in a world without minds there would still be particles and waves of certain sizes and shapes moving in certain ways, but nothing would be "red" or "blue" or "soft" or "loud" or "sweet" or "bitter," etc.

What Berkeley did is to agree with his predecessors that secondary qualities exist only in the mind and not in independent material objects themselves, but then to assert that the very same considerations establish equally well that the same is true of supposedly primary qualities.

Consider shape. The surface of a table might seem smooth and flat to us, but to a microscopic creature it would be positively mountainous in its unevenness. A stick in water that feels straight to the touch looks bent.

Or consider number. A rubber ball is one item to us, but perceived from another perspective it is countless molecules, or even more atoms.

Is the table "really" flat or uneven? Is the stick "really" straight or bent? Is the ball "really" one thing or many?

Berkeley contends that these things don't "really" have any of these properties, as just like secondary qualities, supposed primary qualities are only in the mind as well.

From there it's only a short step to denying the existence of material objects entirely. For what sense does it make to speak of objects that have no qualities whatsoever? If all of an object's qualities exist only as ideas in a mind, then the object itself has no reality outside of a mind.

By collapsing the distinction between primary and secondary qualities, does Berkeley succeed in establishing that metaphysical idealism is a better causal hypothesis to explain our mental states than any alternative?

Probably not. The problem may lie in the premise that he shares with some of those he's arguing against, namely that any quality that can be perceived differently must exist only in a mind. Perhaps empirical statements are not statements about an independent, material world as it would be without perceivers, nor statements about phenomenon that exist only inside a mind. Perhaps instead empirical statements are about the intersection of a material world and a perceiving mind, and thus depend on, rather than refute, the existence of both.