In the same year, 1837, and in the midst of these occupations, I resumed the _Logic_. I had not touched my pen on the subject for five years, having been stopped and brought to a halt on the threshold of Induction. I had gradually discovered that what was mainly wanting, to overcome the difficulties of that branch of the subject, was a comprehensive, and, at the same time, accurate view of the whole circle of physical science, which I feared it would take me a long course of study to acquire; since I knew not of any book, or other guide, that would spread out before me the generalities and processes of the sciences, and I apprehended that I should have no choice but to extract them for myself, as I best could, from the details. Happily for me, Dr. Whewell, early in this year, published his _History of the Inductive Sciences_. I read it with eagerness, and found in it a considerable approximation to what I wanted. Much, if not most, of the philosophy of the work appeared open to objection; but the materials were there, for my own thoughts to work upon: and the author had given to those materials that first degree of elaboration, which so greatly facilitates and abridges the subsequent labour. I had now obtained what I had been waiting for. Under the impulse given me by the thoughts excited by Dr. Whewell, I read again Sir J. Herschel's _Discourse on the Study of Natural Philosophy_: and I was able to measure the progress my mind had made, by the great help I now found in this work--though I had read and even reviewed it several years before with little profit. I now set myself vigorously to work out the subject in thought and in writing. The time I bestowed on this had to be stolen from occupations more urgent. I had just two months to spare, at this period, in the intervals of writing for the _Review_. In these two months I completed the first draft of about a third, the most difficult third, of the book. What I had before written, I estimate at another third, so that one-third remained. What I wrote at this time consisted of the remainder of the doctrine of Reasoning (the theory of Trains of Reasoning, and Demonstrative Science), and the greater part of the Book on Induction. When this was done, I had, as it seemed to me, untied all the really hard knots, and the completion of the book had become only a question of time. Having got thus far, I had to leave off in order to write two articles for the next number of the _Review_. When these were written, I returned to the subject, and now for the first time fell in with Comte's _Cours de Philosophie Positive_, or rather with the two volumes of it which were all that had at that time been published. My theory of Induction was substantially completed before I knew of Comte's book; and it is perhaps well that I came to it by a different road from his, since the consequence has been that my treatise contains, what his certainly does not, a reduction of the inductive