Matter, Causation, and Determinism
It is in considering the notion of matter that the significance of our definitions is completely established; for matter cannot be a cause, and yet the behaviour of matter is completely determined. According to Russell, the two dogmas that constitute the essence of materialism are: the sole reality of matter and the reign of law. Russell realizes that a belief in determinism is a belief in necessary connection. The identification of space and body means not only that all extension is body, but that a body is merely a region of space. Since Descartes both asserted the existence of body and denied the existence of a vacuum, his notion of the existence of material substance appears to be self-contradictory, and thus meaningless. The causal theory of perception asserts that our perceptions are caused by something external to the perception. The correspondence theory of perception asserts that what causes our perception is identical with what we perceive.