There are, I believe, five main features that serve to distinguish traditional metaphysics from other forms of enquiry. These are: the aprioricity of its methods; the generality of its subject-matter; the transparency or ‘non-opacity’ of its concepts; its eidicity or concern with the nature of things; and its role as a foundation for what there is. In claiming that these are distinguishing features, I do not mean to suggest that no other forms of enquiry possess any of them. Rather, in metaphysics these features come together in a single package and it is the package as a whole rather than any of the individual features that serves to distinguish metaphysics from other forms of enquiry.

It is the aim of this chapter to give an account of these individual features and to explain how they might come together to form a single reasonably unified form of enquiry. I shall begin by giving a rough and ready description of the various features and then go into more detail about what they are and how they are related.