If this result should be deemed unsatisfactory on account of its vagueness, let it be remembered that nothing is gained on the side of clearness by the converse supposition--viz. that priority should be assigned to the principle of causality. For, if we say it is inconceivable that anything should come into existence without a cause--not even excepting the principle of mind itself--then the question immediately arises--If all volition is caused, what is the cause of volition? What caused this cause? And so on till we arrive at the question, What caused the principle of causality? which is absurd. So that whether we regard mind as prior to cause, or cause as prior to mind, or neither as prior to the other, we arrive at precisely the same difficulty. And the difficulty is a hopeless one, because it concerns the ultimate question of Being as Being, or the final mystery of things. Or, to state the matter in another way. An explanation means the reference of observed effects to known causes, or the inclusion of previously unknown causes among causes better known. Hence it is obvious, from the very meaning of what we call an explanation, that at the base of all possible explanations there must lie a great Inexplicable, which, just because more ultimate than any of our possible explanations, does not itself require to be explained. To suppose that it does require to be explained, would be to suppose, that there is something still more ultimate into which, if known, this Inexplicable could be merged. Hence, unless we postulate an infinite series of possible explanations, there must be a basal mystery somewhere, which, in virtue of its constituting the ground of all possible explanations, cannot be, and does not require to be, itself explained. What is this basal mystery? Materialism supposes it to be lodged in Matter to the exclusion of Mind, while Idealism in its extreme forms takes the converse view. Theism supposes that it is an intelligent Person, who is held--and logically enough--not to be able to give any explanation of his own existence; he is, as it is said, self-existent, and, if asked to give any account of his being, would only be able to restate the fact of his being in the words, 'I am that I am.' Lastly, Pantheism, or Monism, supposes the ultimate mystery to be lodged in the universe as a whole. Now, in the present connexion the question before us is simply this--Are we to regard the principle of causality or the principle of mind as the ultimate mystery? And to this question I answer that to me it appears most reasonable to assign priority to mind. For, on the one hand, our only knowledge of causation is empirical, while even as such it is only possible in the same way as our knowledge of objective existence in general is possible--namely, by way of inference from our own mental modifications, which therefore must necessarily have priority so far as we are ourselves concerned. Next, on the other hand,