Even a casual comparison of the table of contents of the present collection with that of its predecessor will reveal significant differences as well as much overlap. By and large, the present selection is the product of two forces: (a) comments from users of the first edition (and from potential users of the second) and (b) our own sense of the direction the field has taken during the past two decades.

We are grateful to our many friends and colleagues, too numerous to thank individually, who have commented on what they found useful and less than useful in our first effort, as well as on what they felt it would be good to have available in one volume. Their perspective has been invaluable, though the responsibility for our selections remains largely our own.

Needless to say, we would have liked in a way to reissue the first edition and simply add a second, companion, volume. But we are deterred by the prohibitive cost (to the user) of the two volumes. Hence the inevitable compromise: A selection was made, omitting several things to make room for new ones. In a number of cases (most notably the Wittgenstein material and “Two Dogmas of Empiricism”), the (present) availability of most of the material enabled us to omit it with less of a sense of loss. Not so with the rest. The selection of new material was even more difficult, as these years have been particularly fecund, both in relevant semi-technical results and in philosophical explorations.