3. However limited may be the direct and immediate result of these investigations, they are of incalculable advantage. It is highly important to acquire science, but not less important to know its limits. Near these limits there are shoals which the navigator ought to know. It is by examining the question of certainty that we ascertain the limits of human science. In descending to the depths to which these questions lead us, the understanding grows dim, and the heart is awed with a religious fear. A moment ago we were contemplating the edifice of human knowledge, and grew proud to see it with its colossal dimensions, its beautiful forms, its fine and bold construction; we enter it, and are led through deep caverns, and, as if by enchantment, the foundation seems to be subtilized, to evaporate, and the superb edifice remains floating in the air. 4. It must be remarked that in entering on the examination of the question of certainty, we do not conceal from ourselves its difficulties. To conceal would not be to solve them; on the contrary, the first condition necessary to their complete solution, is to see them with perfect clearness, and to feel their full force. It is no humiliation to the human understanding to seek those limits beyond which it cannot pass, but it is to elevate and confirm it. Thus the intrepid naturalist, when in search of some object he has penetrated to the bowels of the earth, feels a mixture of terror and pride to be thus buried in subterranean caverns, with just light enough to see immense masses barely suspended above his head and unfathomable abysses beneath his feet. There is something sublime, something attractive and captivating in the obscurity of the mysteries of science, in uncertainty itself, in the very assaults of doubt, threatening to destroy in one instant the work accomplished by the human mind only in the space of long ages. The greatest men have at all times enjoyed the contemplation of these mysteries. The genius which spread its wings over the east, over Greece and Rome, over the schools of the Middle Ages, is the same we now behold in modern Europe. Plato, Aristotle, St. Augustine, Abelard, St. Anselm, St. Thomas of Aquin, Luis Vives, Bacon, Descartes, Malebranche, and Leibnitz, all, each in his own way, felt the sublime inspiration of philosophy. Whatever tends to raise man to lofty contemplation in the sanctuary of his soul, contributes to his aggrandizement; for it separates him from natural objects, reminds him of his noble origin, and proclaims to him his high destiny. In a mechanical and sensual age, when every thing seems opposed to the activity of the powers of the soul, except when they administer to the wants of the body, it is well to renew those great questions in which the mind roams free and untrammelled over unbounden realms of space.