The only motive for commencing a study upon a very old writer is a desire to work out a subject historically; which, in some instances may be allowed, but not very often. In Politics, Ethics, and Rhetoric, the plan might have its advantages; but, with this imperative condition, that we shall follow out the development in the modern works. In proportion as a subject assumes a scientific shape, it must carefully define its terms, marshal its propositions in proper dependence, and offer strict proof of all matters of fact; now, in these respects, every known branch of knowledge has improved with the lapse of ages; so that the more recent works are necessarily the best for entering upon the study. A historical sequence may be proper to be observed; but that should be backward and not forward. The earlier stages of some subjects are absolutely worthless; as, for example, Physics, Chemistry, and most of Biology, in other subjects, as Politics and Ethics, the tentatives of such men as Plato and Aristotle have an undying value; nevertheless, the student should not begin, but end, with them. * * * * * There is an extreme form of putting our present doctrine that runs it into paradox: namely, the one-book-and-no-more maxim. Scarcely any book in existence is so all-sufficient for its purpose that a student is better occupied in re-reading it for the tenth time, than in reading some others once. Even the merits of the one book are not fully known unless we compare it with others; nor have we grasped any subject unless we are able to see it stated in various forms, without being distracted or confused. It is not a high knowledge of horsemanship that can be gained by the most thorough acquaintance with one horse. [NO WORK ENTIRELY SELF-SUFFICIENT.]