By certain intellectual operations, man acquires the knowledge of a series of facts,--he remembers them,--he separates and classifies them,--and forms them into new combinations. But, with the most active exercise of all these operations, his mind might present an accumulation of facts, without order, harmony, or utility;--without any principle of combination, or combined only in those fantastic and extravagant forms which appear in the conceptions of the maniac. It is Reason that reduces the whole into order and harmony,--by comparing, distinguishing, and tracing their true analogies and relations,--and then by deducing truths as conclusions from the whole. It is in this manner particularly, that a man acquires a knowledge of the uniform actions of bodies on each other,--and, confiding in the uniformity of these actions, learns to direct his means to the ends which he has in view. He knows also his own relations to other sentient beings,--and adapts his conduct to them, according to the circumstances in which he is placed,--the persons with whom he is connected,--and the objects which he wishes to accomplish. He learns to accommodate his measures to new circumstances as they arise,--and thus is guided and directed through his physical relations. When reason is suspended, all this harmony is destroyed. The visions of the mind are acted upon as facts; things are combined into fantastic forms, entirely apart from their true relations;--conduct is widely at variance with what circumstances require;--ends are attempted by means which have no relation to them;--and the ends themselves are equally at variance with those which are suitable to the circumstances of the individual. Such is the maniac, whom accordingly we shut up, to prevent him from being dangerous to the public;--for he has been known to mistake so remarkably the relation of things, and the conduct adapted to his circumstances, as to murder his most valuable friend, or his own helpless infant.