The object of the following treatise is to furnish, not only for College classes, but especially for our Academies and High Schools a complete system of Mental Science. Two facts render the treatises in common use unadapted, particularly to the two purposes last named. Such treatises, in the first place, are too large for common use. Then, with hardly any exceptions, they treat of but one department of the mind, the Intellect. The object of the following treatise is to remedy both these defects-to furnish a work sufficiently ample for a clear elucidation of the whole subject, and, at the same time, so concise as not to over burden the mind of the pupil, on the one hand, and, on the other, to furnish a full knowledge of the entire system of Mental Science, the Philosophy, not of the Intellect merely, but also of the Sensibility and Will. It is fully believed by the Author, and he states this as the result of some thirty years' experience in teaching the science, that every pupil, not only in our College classes, but every advanced student in our Academies and High Schools, is capable of fully mastering this treatise, and that when he has done so, he will have attained not only to a distinct understanding of the different faculties of the mind, but also of the varied functions of each of those faculties. ASA MAHAN (1799-1889) was America's foremost Christian educator, reformer, philosopher, and pastor. He was founding president of two colleges and one university, where he was able to inspire numerous reforms, publish authoritative philosophical texts, and promote powerful revivals like his close associate Charles Finney. He led the way on all important fronts while being severely persecuted. He introduced the new curriculum later adopted by Harvard, was the first to instruct and grant liberal college degrees to white and colored women, advised Lincoln during the Civil War, and among many other remarkable achievements, was a father to the early evangelical and holiness movements.