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subordinate sciences is increased, as wider laws are, in their several provinces, gradually revealed to observation and experiment,—if the discovery of gravitation, for instance, is perceived to be valuable because it has illustrated the whole region of mechanics—this analogy may help to explain the effect, upon what we may call the style in which we hold every kind of knowledge, of a habit of intimacy with those highest laws, which, as ultimate propositions, mark the frontier that may not be passed by the human intellect. The progress of physical discovery upon this planet has become more enlightened since men have learned its figure, and the limits within which their exploration has been confined by the Creator. The fears of the followers of Columbus are now unknown, nor is El Dorado any longer searched for. In like manner, the more nearly the metaphysician is able to find the precise sphere within which our researches must be confined, the more successfully may we expect knowledge to be converted into science, and the more submissive should be our reverence, when we turn to those mysteries which are created for us by the limitations of human thought, which are disclosed to metaphysical investigation. The elements of philosophical faith—or, in the language of Reid, the principles of common sense—which are acted on by all, but to which the metaphysician alone directs an intelligent attention, as the special objects of his own science, are the materials of the foundation on which must rest that Classification of the Sciences, towards which “Advance-