We may sum up the matter by saying that the reality of sensible phenomena consists in the constancy of the mutual order in which they exist, and in the dependence of this order upon the divine Intelligence and Will. In this respect, at least, Leibniz resembles the young Irish idealist, Berkeley, who only seven years after Leibniz wrote the "New Essays" composed his "Principles of Human Knowledge," urging that the immediate reality of sense-phenomena consists in their "steadiness, order, and coherence," "in a constant uniform working," and that this "gives us a foresight which enables us to regulate our actions for the benefit of life." It was Berkeley also who wrote that their ultimate reality consists in their being ideas of a Divine Spirit. This was six years before the death of Leibniz. Yet it does not appear that Berkeley knew of Leibniz, and the only allusion to Berkeley which I have found in the writings of Leibniz shows that Leibniz knew only of that caricature of his views which has always been current,--that Berkeley was one who denied the existence of any external world. What he writes is as follows: "As for him in Ireland who questions the reality of 'bodies,' he seems neither to offer what is rational, nor sufficiently to explain his own ideas. I suspect that he is one of those men who are desirous of making themselves known through paradoxes." CHAPTER IX. SOME FUNDAMENTAL CONCEPTIONS. The fundamental category of Locke, as of all who take simply a mechanical view of experience, is that of substance. He had good reason to be surprised when the Bishop of Worcester objected that Locke wished "to discard substance out of the world." How can that be so, Locke asks, when I say that "our idea of body is an extended solid substance, and our idea of soul is of a substance that thinks." And he adds, "Nay, as long as there is any simple idea or sensible quality left, according to my way of arguing, substance cannot be discarded." Everything that really exists, is, according to Locke, substance. But substance to Locke, as again to all who interpret the universe after sensible categories, is unknowable. For such categories allow only of external relations; they admit only of static existence. Substance, in this way of looking at it, must be distinct from its qualities, and must be simply the existing substratum in which they inhere.