Philosophy: A Very Short Introduction

it to believe Berkeley’s denial of matter, a convincing proof that he just couldn’t be right has been extremely elusive. I myself don’t believe that there is one—though neither, you won’t be surprised to hear, do I believe Berkeley.
Some philosophical systems (like Hegel’s) qualify as idealism not because they deny the very existence of matter but because they regard it as subordinate to the mental or spiritual, which is what really determines the nature of reality and gives it purpose. This use of ‘idealism’ parallels the use of ‘materialism’ we noticed above, in its application to the philosophy of Karl Marx. But when we come to the everyday notion of idealism the parallel with ‘materialism’ fails. A materialist’s attention is fixed on material goods as opposed to mental, spiritual, or intellectual ones; whereas an idealist is not someone always focused on the latter rather than the former, but someone committed to ideals. And ideals are essentially things of the mind, because they are the thoughts of circumstances not in fact found in reality, but which we can strive to approach as nearly as the conditions of life permit. The mental nature of ideals makes the connection between the everyday usage of the word and the technical one.
Two more ‘isms’ of which one hears a lot, and which tend to occur together as a pair of supposed opposites, are ‘empiricism’ and ‘rationalism’. Whereas ‘dualism’, ‘materialism’, and ‘idealism’ belong to metaphysics (what sorts of thing are there?), this pair belongs squarely to epistemology (how do we know?).
10. Every subject talks its own talk.
In a rough and ready way we all make a distinction between perceiving and thinking. It is one thing to see the objects on your table, notice that one is a pen and one a computer; it is another thing to think about them, wonder if they still work, or what to do if they don’t. And we are used to the idea that astronomers spend long hours looking at the sky, whereas mathematicians just seem to sit there working things out, feeling no need to look at anything at all except what they themselves have written down. So here, on the face of it, are two quite different ways of acquiring knowledge. Some philosophers have favoured one of them at the expense of the other: ‘empiricism’ is a very general word for doctrines that favour perceiving over thinking, ‘rationalism’ for doctrines that favour thinking over perceiving.
There may have been philosophers who held that only what could be perceived could be known, so allowing no cognitive powers at all to thought, inference, and reason. Something of much that kind is reported of the Lokāyatas, whom we met above in connection with materialism. According to some reports of their thinking they went even further, saying that only what can be perceived exists. If so (but remember that all the reports we have were written by their opponents!), they surely overreached themselves. Nobody who thinks that knowledge is only of what you have perceived can claim to know that nothing imperceptible exists, since that isn’t something you could possibly perceive. (It would make as much sense as claiming to be able to hear that nothing inaudible exists.)
An empiricist who holds that only perception yields knowledge need not be saying that the process of perception itself involves no thought whatever, so that we can have as it were pure perception untainted by any thinking. Even to look at my table and see that there is a pen on it requires more of me than just passively registering the light patterns that enter my eyes. I need to know a little about pens, at the very least about what they look like, and then bring this knowledge to bear, otherwise I shall no more see a pen than does the camera with which we photograph the pen. Perception is interpretative, whereas cameras merely record patterns of light. So a less crude empiricism will allow that classification, thought, inference, and reason all have their legitimate role. But it will take its stand on the point that they cannot generate a single item of knowledge on their own. It may be true that there is no thought-free perception; but it is also true that there is no perception-free knowledge. All claims to knowledge answer, in the end, to perception; it may be possible for them to go beyond perception, but they must start from it.
The empiricist can offer a powerful argument for this view; any would-be rationalist must have an answer ready. In perception we are in some kind of contact with objects around us; they have an effect on our senses. But if we try to think in complete independence of perception, where is the link between us and the objects we are trying to think about? For if there is no such link, then there is the world, and here are we thinking away to ourselves. That sounds like a recipe for pure fantasy, perhaps interspersed with the very occasional lucky guess. Let us take a quick look at how three philosophers of strongly rationalist tendencies, Plato, Kant, and Hegel, responded to this challenge.
What reason can tell us, according to Plato, is not directly about the world of the senses at all, but about eternal, transcendent entities called Ideas or Forms: the Good, the Just, the Equal, the Beautiful. Things we perceive with the senses are good, equal, and so on just in so far as they ‘participate’ in these Forms or approximate to the standards set by them. But how does Reason get its knowledge of the Forms? Plato (as you will know by now if you took my advice to read his Phaedo as a follow-up to Crito) made use of a belief far from unknown to ancient Greek thought. The soul has existed before it entered its present body. In that existence it encountered—Plato hints obscurely at something analogous to perception—the Forms, and in rational thought it is now