At most of our American Colleges there are Clubs formed by the students devoted to particular branches of learning; and these clubs have the laudable custom of inviting once or twice a year some maturer scholar to address them, the occasion often being made a public one. I have from time to time accepted such invitations, and afterwards had my discourse printed in one or other of the Reviews. It has seemed to me that these addresses might now be worthy of collection in a volume, as they shed explanatory light upon each other, and taken together express a tolerably definite philosophic attitude in a very untechnical way.