In my thesis I criticise the most important Causal Theories that have been advanced, and put forward a Causal Theory of my own. In Chapter 1 I describe some of the theories that have been advanced, or criticised, as Causal Theories, and point out that they fall into several distinct types. In Chapter 2 I criticise the sort of Causal Theory that includes the thesis that our knowledge of the physical world is in some sense inferential. In Chapter 3 I argue against the sort of Causal Theory which involves the supposition that sense-data or their like are involved in perception. In Chapter 4 I argue in favour of the sort of Causal Theory which contains the view that the perception of a physical object is a matter of the perceiver's being caused by it to have a sense-experience. In Chapter 5 I argue that the experiential element in perception is not a matter of the perceiver's acquiring or tending to acquire a belief. In Chapter 6 I inquire whether perception must involve the having of a sense-experience which in some sense represents the perceived object, and specify the conditions which the perceptual experience must fulfil. I introduce the expression "have a good representation" in terms of one sense of "seem" and its cognates. In Chapter 7 I conclude that representation enters into perception insofar as the perceived object must bring about the perceiver's sense-experience in a way which I describe as "productive of good representations". I advance my own Causal Theory of Perception, to which this contention is central. In Chapter 8 I support my theory by considering the perception of certain sorts of physical objects that may appear problematical and have been unduly neglected by philosophers in the past.