These essays were written over a fifteen-year period. During that time my views underwent a number of changes, especially on the philosophy of mathematics and on the interpretation of quantum mechanics. Nevertheless they have, I believe, a certain unity.

The major themes running through these essays, as I look at them today, are the following: (i) Realism, not just with respect to material objects, but also with respect to such ‘universals’ as physical magnitudes and fields, and with respect to mathematical necessity and mathematical possibility (or equivalently with respect to mathematical objects); (2) the rejection of the idea that any truth is absolutely a priori; (3) the complementary rejection of the idea that ‘factual’ statements are all and at all times ‘empirical’, i.e. subject to experimental or observational test; (4) the idea that mathematics is not an a priori science, and an attempt to spell out what its empirical and quasi-empirical aspects really are, historically and methodologically.

Realism

These papers are all written from what is called a realist perspective. The statements of science are in my view either true or false (although it is often the case that we don't know which) and their truth or falsity does not consist in their being highly derived ways of describing regularities in human experience. Reality is not a part of the human mind; rather the human mind is a part – and a small part at that – of reality. But no paper in this collection is entirely devoted to the topic of realism, for my interest in the last fifteen years has not been in beating my breast about the correctness of realism, but has rather been in dealing with specific questions in the philosophy of science from a specific realist point of view.