exposition came to be written, I found that I had so much over-estimated my agreement with him, and he dissented so much from the most original of the two Essays, that on International Values, that I was obliged to consider the theory as now exclusively mine, and it came out as such when published many years later. I may mention that among the alterations which my father made in revising his _Elements_ for the third edition, several were founded on criticisms elicited by these conversations; and in particular he modified his opinions (though not to the extent of our new speculations) on both the points to which I have adverted. When we had enough of political economy, we took up the syllogistic logic in the same manner, Grote now joining us. Our first text-book was Aldrich, but being disgusted with its superficiality, we reprinted one of the most finished among the many manuals of the school logic, which my father, a great collector of such books, possessed, the _Manuductio ad Logicam_ of the Jesuit Du Trieu. After finishing this, we took up Whately's _Logic_, then first republished from the _Encyclopedia Metropolitana_, and finally the _Computatio sive Logica_ of Hobbes. These books, dealt with in our manner, afforded a high range for original metaphysical speculation: and most of what has been done in the First Book of my _System of Logic_, to rationalize and correct the principles and distinctions of the school logicians, and to improve the theory of the Import of Propositions, had its origin in these discussions; Graham and I originating most of the novelties, while Grote and others furnished an excellent tribunal or test. From this time I formed the project of writing a book on Logic, though on a much humbler scale than the one I ultimately executed. Having done with Logic, we launched into Analytic Psychology, and having chosen Hartley for our text-book, we raised Priestley's edition to an extravagant price by searching through London to furnish each of us with a copy. When we had finished Hartley, we suspended our meetings; but my father's _Analysis of the Mind_ being published soon after, we reassembled for the purpose of reading it. With this our exercises ended. I have always dated from these conversations my own real inauguration as an original and independent thinker. It was also through them that I acquired, or very much strengthened, a mental habit to which I attribute all that I have ever done, or ever shall do, in speculation: that of never accepting half-solutions of difficulties as complete; never abandoning a puzzle, but again and again returning to it until it was cleared up; never allowing obscure corners of a subject to remain unexplored, because they did not appear important; never thinking that I perfectly understood any part of a subject until I understood the whole.