Mill's _Logic_ or so instructive and interesting a book as Professor Jevons's _Principles of Science_, a certain number at any rate of the bad mental habits of people would be cured; and for those of you here who have leisure enough, and want to find a worthy keystone of your culture, it would be hard to find a better thing to do for the next six months than to work through one or both of the books I have just named--pen in hand. The ordinary text-books of formal logic do not seem to meet the special aim which I am now trying to impress as desirable--namely, the habit of valuing, not merely speculative nor scientific truth, but the truth of practical life; a practising of the intellect in forming and expressing the opinions and judgments that form the staple of our daily discourse. It is now accepted that the most effective way of learning a foreign language is to begin by reading books written in it, or by conversing in it--and then after a certain empirical familiarity with vocabulary and construction has been acquired, one may proceed to master the grammar. Just in the same way it would seem to be the best plan to approach the art of practical reasoning in concrete examples, in cases of actual occurrence and living interest; and then after the processes of disentangling a complex group of propositions, of dividing and shifting, of scenting a fallacy, have all become familiar, it may be worth while to find names for them all, and to set out rules for reasoning rightly, just as in the former illustration the rules of writing correctly follow a certain practice rather than precede it.