This course reviews central issues in theory of meaning, in particular the relation between meaning and reference to objects. What explains our ability to refer to objects? Is the ability to think about an object a matter of standing in an appropriate causal relation to it? And if we take this view, does it help us to understand how thought might be in the end a biological phenomenon? We will look at basic lines of thought set out here by Kripke and Putnam, and theorists such as Evans and Dretske who have built on their ideas. We will also look at the contrasting view of meaning and reference presented by the later Wittgenstein. We will begin, however, with the classical views of Frege and Russell.