"The faith which can not stand unless buttressed by contradictions is built upon the sand. The profoundest faith is faith in the unity of truth. If there is found any conflict in the results of a right reason, no appeal to practical interests, or traditionary authority, or intuitional or theological faith, can stay the flood of skepticism."--ABBOT. In the previous chapter we have considered the answers to this question which are given by the Idealistic and Materialistic schools; it devolves upon us now to review (iii.) the position of the school of _Natural Realism_ or _Natural Dualism_, at the head of which stands Sir William Hamilton. It is admitted by this school that philosophic knowledge is "the knowledge of effects as dependent on their causes,"[278] and "of qualities as inherent in substances."[279] [Footnote 278: "Lectures on Metaphysics," vol. i. p. 58.] [Footnote 279: Ibid., vol. i. p. 138.] 1. _As to Events and Causes_.--"Events do not occur isolated, apart, by themselves; they occur and are conceived by us only in connection. Our observation affords us no example of a phenomenon which is not an effect; nay, our thought can not even realize to itself the possibility of a phenomenon without a cause. By the necessity we are under of thinking some cause for every phenomenon, and by our original ignorance of what particular causes belong to what particular effects, it is rendered impossible for us to acquiesce in the mere knowledge of the fact of the phenomenon; on the contrary, we are determined, we are necessitated to regard each phenomenon as _only partially known until we discover the causes_ on which it depends for its existence.[280] Philosophic knowledge is thus, in its widest acceptation, the knowledge of effects as dependent on causes. Now what does this imply? In the first place, as every cause to which we can ascend is only an effect, it follows that it is the scope, that is, the aim, of philosophy to trace up the series of effects and causes until we arrive at _causes which are not in themselves effects_,"[281]--that is, to ultimate and final causes. And then, finally, "Philosophy, as the knowledge of effects in their causes, necessarily tends, not towards a plurality of ultimate or final causes, but towards _one_ alone."[282] [Footnote 280: Ibid., vol. i. p. 56.] [Footnote 281: "Lectures on Metaphysics," vol. i. p. 58.] [Footnote 282: Ibid., vol. i. p. 60.]