If any apology were necessary for adding yet another to the numerous works on Mental Philosophy which have recently appeared, the circumstances that led to the preparation of the present volume may, perhaps, constitute that apology.

When called, several years since, to the chair of Mental and Moral Philosophy, in this Institution, the text-books, then in use, seemed to me not well adapted to the wants of College students. Nor was it easy to make a change for the better. Of the works in this department, then generally in use in our Colleges, some presumed on a more extensive acquaintance with the science than most young men at this stage of education are likely to possess; others, again, erring on the opposite extreme, were deficient in thorough and scientific treatment; while most, if not all, were, at the best, incomplete, presenting but a partial survey of the entire field. In none of them was the science of mind presented in its completeness and symmetry, in a manner at once simple, yet scientific; in none of them, moreover, was it brought down to the present time. Something more complete, more simple, more thorough, seemed desirable.

Every year of subsequent experience as a teacher has but confirmed this impression, and made the want of a book better adapted to the purposes of instruction, in our American Colleges, more deeply felt. The works on mental science, which have recently appeared in this country, while they are certainly a valuable contribution to the department of philosophy, seem to meet this deficiency in part, but only in part. They traverse usually but a portion of the ground which Psychology legitimately occupies, confining their attention, for the most part, to the Intellectual Faculties, to the exclusion of the Sensibilities, and the Will.

Feeling deeply the want which has been spoken of, it seemed to me, early in my course, that something might be done toward remedying the deficiency, by preparing with care, and delivering to the classes, lectures upon the topics presented in the books, as they passed along. This course was adopted—a method devolving much labor upon the instructor, but rewarding him by the increased interest and more rapid progress of the pupils. Little by little the present work thus grew up, as the result of my studies, in connection with my classes, and of my experience in the daily routine of the recitation and lecture room. Gradually the lectures, thus prepared, came to take the place more and more of a textbook, until there seemed to be no longer any reason why they should not be put into the hands of the student as such.

It is much easier to decide what a work on mental science ought to be, than to produce such a work. It should be comprehensive and complete, treating of all that properly pertains to Psychology, giving to every part its due proportion and development. It should treat the various topics presented, in a thorough and scientific manner. It should be conversant with the literature of the department, placing the student in possession, not only of the true doctrines, but, to some extent also, of the history of those doctrines, showing him what has been held and taught by others upon the points in question. In style it should be clear, perspicuous, concise, yet not so barren of ornament as to be destitute of interest to the reader.

At these qualities the writer has aimed in the present treatise; with what success, others must determine.

All science, in proportion as it is complete and true, becomes simple. In proportion as this result is attained, the labor bestowed upon it disappears from view, and the writer seems, perhaps, to others, to have said but a very plain and common thing. This is peculiarly the case with mental science. The difficulty of discussing with clearness and simplicity, and, at the same time, in a complete and thorough manner, the difficult problems of Psychology, will be understood only by those who make the attempt.

J. H.