Mental Science, in the forms under which it usually exhibits itself, is a subject of extreme generality. It deals with the phenomena of consciousness, as these are common to the whole human race. It hardly takes into account those peculiarities of the mind, from which individual character is formed; nevertheless, in the practical application of mental science, it is with individual character that we are for the most part engaged. Shall we, then, conclude that the prevailing systems of mental science afford no insight into the practical uses of that science ? Certainly not—and for this very sufficient reason, that the peculiarities of individual minds bear but a very small proportion to the operations which arise in obedience to laws affecting all the sound-minded members of our race. Hence, in the study of the practical uses of mental science, while it is incumbent upon us to fix a strict attention on the general laws of thought, means must at the same time be sought to bring to light the limits of the range, within which these laws, in particular minds, suffer modification.