Yet metaphysics, like philosophy as a whole, is not something which can simply be cured or abandoned, as if it were an intellectual disease. The most antimeta-physical philosophers have, in fact, a tacit metaphysics of their own, which lurks behind the assertion that all experience and all knowledge must be of classes, and of contrasts and comparisons between them. To put it in the simplest way, they will allow that I can know and speak sensibly about something white, since I know . white by contrast with black, and by comparison with red, orange, yellow, green, blue, indigo, and violet. They will allow meaningful statements about dogs and cats, because they are organic as distinct from inorganic, mammals as distinct from marsupials, and, though frisky, have clearly defined boundaries which demark them from the whole word of non-dogs and non-cats. But the underlying assumption, that all knowledge is in terms of contrasts, is as metaphysical as an assumption can be.