explanations offered by Whately and others, though they might give a temporary satisfaction, always, in my mind, left a mist still hanging over the subject. At last, when reading a second or third time the chapters on Reasoning in the second volume of Dugald Stewart, interrogating myself on every point, and following out, as far as I knew how, every topic of thought which the book suggested, I came upon an idea of his respecting the use of axioms in ratiocination, which I did not remember to have before noticed, but which now, in meditating on it, seemed to me not only true of axioms, but of all general propositions whatever, and to be the key of the whole perplexity. From this germ grew the theory of the Syllogism propounded in the Second Book of the Logic; which I immediately fixed by writing it out. And now, with greatly increased hope of being able to produce a work on Logic, of some originality and value, I proceeded to write the First Book, from the rough and imperfect draft I had already made. What I now wrote became the basis of that part of the subsequent Treatise; except that it did not contain the Theory of Kinds, which was a later addition, suggested by otherwise inextricable difficulties which met me in my first attempt to work out the subject of some of the concluding chapters of the Third Book. At the point which I had now reached I made a halt, which lasted five
