In using the above terms, let it not be supposed that I mean to imply by the one a perfect knowledge, or a knowledge of everything, and by the other a perfect ignorance, or a total want of any knowledge. Either of such conditions of the mind is incompatible with human organization; the one, a perfect knowledge, belongs alone to an order of intelligence infinitely excelling that of man; and the other, a perfect ignorance, must be sought for in creatures so far below him as to possess no intelligence. The idiot is not without perception and knowledge, though of an imperfect and irregular kind. The dog knows its master, recognizes and obeys his voice. The horse knows and traces, after years of absence, the road he had once been accustomed to travel; and even reptiles and fishes acquire a knowledge of persons, of times, and of things; all this being independent of that range of intelligences which has been given to every creature for the preservation of its own existence, and for ensuring the continuance of its species. The terms Knowledge and Ignorance are used, then, in a comparative sense, being, according to circumstances, convertible one into the other. What, for instance, is knowledge at one time, becomes ignorance at another; and the man who seems wise to those who know less than he does, seems equally foolish to those who know more--a strong reason surely why no one, however gifted he may to himself appear, should despise his less gifted brethren. Mounted he may indeed be on a hill so high that he can discern objects in the distance which are hidden from the more humble plodders of the plain below, and yet his own horizon be proportionately limited when compared to that of others who have climbed the still higher mountain above him. Can we not all bring home to our minds this varying value of our acquirements at successive periods of our lives? and are we not sometimes surprised to reflect that some problem was once difficult, or some fact obscure, which is now as familiar to our understandings as the daylight to our eyes? We have, in short, as regards these particular objects, passed from the night of ignorance into the day of knowledge. And us with the same individual, and even with whole classes of individuals, at different epochs, so is it with different individuals at the same time: one person holding in his hand the dim taper of ignorance, sees by its flickering and ill-directed light the object of his examination, distorted by partial and shifting shadows--just as some timid traveller on a dusky night sees in each waving bush, as to his alarmed imagination it grows to a portentous size, or assumes a fearful form, some aërial phantom, or some terrestrial monster. The other, raising the bright lamp of knowledge, dispels at once by its clear and steady light, uncertainty, and sees the object as it is.