Thought must proceed in one of these two directions. The object-matter of thought being composed wholly of attributes can differ only in the presence or absence of certain attributes. A combination, then, of these two movements must complete the intellectual orbit. The direction of the movement of the mind will be determined by the end proposed. When we possess the knowledge of phenomena and wish to discover law--that is, when we seek information--we proceed by induction, from the individual to the general. When possessed of knowledge, we wish to discover its applications, when knowing the law, we wish to determine the phenomena necessarily resulting therefrom, we proceed by deduction--from the general to the individual. Complete knowledge, then, consists in the highest possible generalization, and the expansion of this term into a series, ending only with the last possible individualization. The aim of physical science is to determine that half of the intellectual orbit which lies between the individual and the general--the aim of metaphysical science is to trace the other half which lies between the general and the individual. When we seek to know what is, we proceed by induction--the method of the phenomenal. When, knowing what is, we proceed to determine what hence must be, we proceed by deduction--the method of the Necessary. Thus Science, at first seeking principles, proceeds by induction to establish them; but after these fundamental principles have been established, it proceeds deductively to determine what must result from them, without waiting to discover these truths by observation. Knowledge is thus complete just in proportion to the extension of its scope through generalization. The higher the generalization, the more inclusive will it be, and the _summum genus_, or the final generalization, will be the highest attainable reach of knowledge. When man can make no further generalization, his knowledge will be, in so far, absolute and complete, and all that remains possible to him will be the practical application of what he already knows. Perfect knowledge is nothing but perfect generalization. The Supreme Intelligence being hypothetically possessed of all knowledge, that is, having discriminated the absolute _summum genus_, can proceed no further in this direction; his intellectual activity must be exerted in a descending series, or from the general towards the individual, and this process must be, as we have seen above, by a determinate series of steps, fixed by the operation of a definite law, which law proceeds by the successive addition of attributes to the general.