Every one is fully aware of the fact, that of all subjects which it concerns man to investigate, that involved in these two questions is of paramount importance, namely, What ought I to be? and, How ought I to act? The scientific solution and elucidation of these questions, constitutes the peculiar sphere of the science of Moral Philosophy. A treatise on Moral Philosophy that does justice to its subject, will, of course, tax to the utmost the powers of the hardest student who attempts fully to fathom the depths, and ascend the heights of thought to which it attains; and at the same time, it will so elucidate that subject, that the ordinary reader who will devote adequate time and attention to its perusal, will study it with much interest and profit. Such it has been the fixed aim of the author to render the following treatise. He designed to render it a book for the student, and at the same time, a book for the people. This treatise was not prepared for the thoughtless, who take up such a work, glance, it may be, at its contents, and then lay it aside, as too deep for them, individuals whose minds float at random upon the surface of things, without looking seriously into the depths beneath, or to the heights above for the purpose of understanding the great realities within and around them, realities among which they are to have their eternal dwelling place, and who especially never ponder the questions, What am I? Where am I? and Whither am I bound? What ought I to be? What ought I to do? and What will be my destiny, as the consequence of being and doing what I ought, or ought not? It was prepared, on the other hand, for thinkers, into whose hearts wisdom has entered, and unto whose souls knowledge is pleasant. ASA MAHAN (1800-1889) 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.