With a few minor alterations, the essays which are collected in this volume are reprinted in their original form. Since many of the problems with which they deal are inter-connected, there is a certain amount of repetition, but I hope that it will not be thought excessive. I do not think that there are any serious inconsistencies, though the short paper on 'The Identity of Indiscernibles' raises doubts about the thesis of the paper on 'Individuals': this is, indeed, my reason for including it. While I have not reprinted anything that I now believe to be false, I should certainly not claim that all the questions treated had been satisfactorily disposed of. In particular, I think that there is still much work to be done on the subject of 'Basic Propositions' and on that of 'Freedom and Necessity'. I am more confident about the results obtained in the essay on 'Statements about the Past', and I have used them in making yet another attack on the vexatious problem of 'One's Knowledge of Other Minds'. In both these cases I am much indebted, at least as regards the manner of approach, to the writings of Professor Wisdom.
In the second edition of The Philosophy of G. E. Moore, Professor Moore has written an addendum to his 'Reply to my Critics', in which he raises some strong objections to the criticisms that I make of certain of his views in my paper on 'The Terminology of Sensedata'. I have added two long footnotes to this paper in . . .