The fit *objects of knowledge* vary indefinitely with one’s condition in life. Things in themselves trivial or evanescent may, under certain circumstances, claim our careful attention and thorough cognizance. We ought, on the one hand, to know all we can about matters concerning which we must speak or act, and, on the other hand, to refrain from voluntarily speaking or acting in matters of which we are ignorant. Thus our social relations and our daily intercourse may render it incumbent on us to obtain for current use a large amount of accurate knowledge which is not worth our remembering. Then a man’s profession, stated business, or usual occupation opens a large field of knowledge, with which and with its allied provinces it is his manifest duty to become conversant to his utmost ability; for the genuineness and value of his work must be in a great degree contingent on his intelligence. At the same time, every man is bound to make his profession worthy of respect; in failing to do so, he wrongs and injures the members of his profession collectively; and no calling can obtain respect, if those who pursue it show themselves uncultivated and ignorant. Thus far, then, should knowledge be extended on grounds of practical utility. Beyond and above this range, there is an unlimited realm of truth, the knowledge of which is inestimably precious for the higher culture of the mind and character. In this realm, of which only an infinitesimal portion can be conquered during an earthly lifetime, there is no unfruitful region,—there is no department of nature, of psychology, or of social science, through which the mind may not be expanded, exalted, energized, led into more intimate relations with the Supreme Intelligence, endowed with added power of beneficent agency. While, therefore, knowledge of things as they are, and of their underlying principles and laws, so far as we are able to acquire it, is not only a privilege beyond all price, but an absolute duty, there are no moral considerations which need direct or limit our choice of the themes of research or study. These may properly be determined by native or acquired proclivity, by opportunity, or by considerations of usefulness. Nor, if the love of truth be formed and cherished, can it of be of any essential importance whether this or that portion of truth be pursued or neglected during the brief period of our life in this world; for, at best, what we leave unattained must immeasurably exceed our attainments, and there is an eternity before us for what we are compelled to omit here. At the same time, the unbounded scope and the vast diversity of things knowable and worthy to be known are adapted to stimulate self-culture, and in that same proportion to invest human life with a higher dignity, a larger intrinsic value, and a more enduring influence. Section III. Self-Control.