Materialism—A very broad category of philosophy containing many shades of theory. The main points are that everything in existence is only matter in motion. According to some materialists, mind exists, but only as an effect of matter in motion. Other materialists say mind has no existence at all. All agree there is no God, there is no first cause or prime mover and that life is not eternal. All phenomena change, eventually pass out of existence, returning back again to a primordial eternal material ground in an eternal retransformation of matter. Marxists claim to be materialists, but the doctrine taught by Karl Marx has idealistic tendencies. See Idealism, Marxism, Mind/body problem, Scepticism.