The union of profound knowledge with divine faith, and the recognition and perception of their unity, is the mind’s first step within the domain of truth and of the consciousness of it; or, rather, the first step in that gradation by which the mind and consciousness advance toward verity; and it is even the fundamental principle of truth itself that constitutes this beginning. The judgment which discriminates and decides between a simple universal belief in God, and the connection of such a faith with all natural and sublimely true philosophy on the one hand, and unbelief, false science, and the various systems of error on the other, forms the second term or step in the gradual progress of truth and the spirit of truth in the human consciousness, whether of individuals, or of the whole human race, or of any particular period of its development. These two subjects have already occupied our attention in the two preceding Lectures. The third point which the mind must attain to as the spirit of truth is more fully expanded, both in the consciousness and in science, is the profitable application thereof to actual life, or its real manifestation, and the practical carrying out of its principles. For it is by this alone that the divine and fundamental principle of truth, and that important faculty of judgment which separates and distinguishes truth and true science from ignorance and error, are realized, and attain to their full end and perfection. The consideration of this subject will form the basis of the present and all the following Lectures. Before, however, I enter upon this new topic, or attempt to solve this third problem of the actual application of science to life and of its profitable combination therewith, I would wish to add here a few historical remarks on the subject-matter of our last discussions, which, while they serve to complete and to illustrate it, will at the same time furnish a natural and easy transition to our present speculations. The struggle and the alternate triumph of belief and unbelief, as they gained in turn the ascendency over the minds of men, and gave the dominant tone to different ages, or, rather, the contest of truth and true science with the different systems of error in the several periods of the development of mankind and of the history of the human intellect, is at all times a subject of the highest interest for philosophical observation. In historical applications like the present, it invariably proves pre-eminently useful and instructive. I shall, however, confine myself to a few examples, and select such as are most immediately connected with our subject, or seem likely to lead to the most important results.