process to strict rules and to a scientific test, such as the syllogism is for ratiocination. Comte is always precise and profound on the method of investigation, but he does not even attempt any exact definition of the conditions of proof: and his writings show that he never attained a just conception of them. This, however, was specifically the problem, which, in treating of Induction, I had proposed to myself. Nevertheless, I gained much from Comte, with which to enrich my chapters in the subsequent rewriting: and his book was of essential service to me in some of the parts which still remained to be thought out. As his subsequent volumes successively made their appearance, I read them with avidity, but, when he reached the subject of Social Science, with varying feelings. The fourth volume disappointed me: it contained those of his opinions on social subjects with which I most disagree. But the fifth, containing the connected view of history, rekindled all my enthusiasm; which the sixth (or concluding) volume did not materially abate. In a merely logical point of view, the only leading conception for which I am indebted to him is that of the Inverse Deductive Method, as the one chiefly applicable to the complicated subjects of History and Statistics: a process differing from the more common form of the deductive method in this--that instead of arriving at its conclusions by general reasoning, and verifying them by specific experience (as is the natural order in the deductive branches of physical science), it obtains its generalizations by a collation of specific experience, and verifies them by ascertaining whether they are such as would follow from known general principles. This was an idea entirely new to me when I found it in Comte: and but for him I might not soon (if ever) have arrived at it.