little. And in the course of years, when you come to look back, if you have not done what you have heard from your advisers—and among many counselors there is wisdom—you will bitterly repent when it is too late. The habits of study acquired at universities are of the highest importance in after-life. At the season when you are young in years, the whole mind is, as it were, fluid, and is capable of forming itself into any shape that the owner of the mind pleases to allow it, or constrain it, to form itself into. The mind is then in a plastic or fluid state; but it hardens gradually, to the consistency of rock or of iron, and you can not alter the habits of an old man: he, as he has begun, so he will proceed and go on to the last.
By diligence I mean, among other things, and very chiefly, too—honesty, in all your inquiries, and in all you are about. Pursue your studies in the way your conscience can name honest. More and more endeavor to do that. Keep, I should say for one thing, an accurate separation between what you have really come to know in your minds and what is still unknown. Leave all that latter on the hypothetical side of the barrier, as things afterward to be acquired, if acquired at all; and be careful not to admit a thing as known when you do not yet know it. Count a thing known only when it is imprinted clearly on your mind, and has become transparent to you, so that you may survey it on all sides with intelligence. There is such a thing
