IN the successive imprints of this book that have appeared since it was first published in 1869, no changes have been made except the correction of typographical and similar errors. In the present edition several alterations have been made, both in the way of addition and omission. SO far as the form is concerned, the book is still in some respects difierent, perhaps for the better, from what it would be if it were a work freshly prepared by the author. The fundamental principles which it represents ap pear to me, however, no less true, and more impor tant, than they did when it was first written. I still think that Hegel's analysis of logical forms is the only one which represents their true nature; while the philosophy, if it may be so called, which, in the book, underlies the treatment of the processes of thought, has furnished the lines which my own more serious work has ever since followed.