Lewis has had a significant impact in many areas of philosophy. One of his most significant legacies, however, will be in the area of philosophical methodology: how philosophers do philosophy, and how they think about what they are doing. This book is full of examples of Lewis's approach to philosophy, but it is worth explicitly considering some of Lewis's views about how to go about tackling philosophical problems.

Quine and Moore

In Chapter 1, I mentioned some of the ways in which Lewis's philosophy was influenced by Quine's. Lewis is a materialist (at least about this world); the only things we need to believe are found in this world are physical objects, and perhaps sets that have physical objects among their members, if those sets are located here. (If events are sets, for example (see Chapter 3), then sets are among the things we encounter in this world as well.) Lewis is also inclined to think that concrete objects plus mathematical objects such as sets are all we need to explain reality. Aspects of reality such as meaning, morality or necessity are to be explained ultimately in these terms. Unlike Quine, Lewis thinks that we need to distinguish some elite, objectively “natural” properties from the abundant sets. Lewis also thinks that we have to recognize many more concrete objects than Quine does; while Quine is prepared to recognize the existence of objects at other times than the present, he is not prepared to admit the existence of concrete worlds beside the actual.