one whose solution might be taken for granted. On the contrary, it was just this question: How shall we conceive the individual to be related to the universe? which seemed to him to be the nerve of the philosophic problem, the question whose right answer would solve the problems of religion, of morals, of the basis of science, as well as of the nature of reality. The importance of just this way of putting the question had been rendered evident by the predecessors and contemporaries of Leibniz, especially by Descartes, Spinoza, and Locke. His more specific relations to the last-named will occupy us hereafter; at present we must notice how the question stood at the hands of Descartes and Spinoza.
Descartes had separated the individual from the universal. His philosophy began and ended with a dualism. I have just said that the problem of philosophy is the unity of experience. Yet we find that there have been thinkers, and those of the first rank, who have left the matter without discovering any ultimate unity, or rather who have made it the burden of their contention that we cannot explain the world without at least two disparate principles. But if we continue to look at the matter in this historical way, we shall see that this dualism has always been treated by the successors of such a philosopher, not as a solution, but as a deeper statement of the problem. It is the function of dualistic philosophies to re-state the question in a new and more significant way. There are times when the accepted unity of thought is seen to be inadequate and superficial. Men are thrashing old straw, and paying themselves with ideas which have lost their freshness and their timeliness. There then arises a philosopher who goes deep, beyond the superficial unity, and who discovers the untouched problem. His it is to assert the true meaning of the question, which has been unseen or evaded. The attitude of dualism is thus always necessary, but never final. Its value is not in any solution, but in the generality and depth of the problem which it proposes, and which incites thought to the discovery of a unity of equal depth and comprehensiveness.
Except for Descartes, then, we should not be conscious of the gulf that yawns between the individual mind and the universe in front of it. He presented the opposition as between mind and matter. The essence of the former is thought; of the latter, extension. The conceptions are disparate and opposed. No interaction is possible. His disciples, more consistent than their master, called in a deus ex machina,—the miraculous intervention of God,—in order to account for the appearance of reciprocal action between the universe of matter and the thinking individual. Thus they in substance admitted the relation between them to be scientifically inexplicable, and had recourse to the supernatural. The individual does not act upon the universe to produce, destroy, or alter the arrangement of anything. But upon the occasion of his volition God produces a corresponding material change. The world does not act upon the soul of the individual to produce thoughts or sensations. God, upon occasion of the external affection, brings them into being. With such thoroughness Descartes performed his task of separation. Yet the introduction of the deus ex machina only complicated the problem; it introduced a third factor where two were already too many. What is the relation of God to Mind and to Matter? Is it simply a third somewhat, equally distinct from both, or does it contain both within itself?
Spinoza attempted to solve the problem in the latter sense. He conceived God to be the one substance of the universe, possessing the two known attributes of thought and matter. These attributes are one in God; indeed, he is their unity. This is the sole legitimate outcome of the Cartesian problem stated as Descartes would have it stated. It overcomes the absoluteness of the dualism by discovering a common and fundamental unity, and at the same time takes the subject out of the realm of the miraculous. For the solution works both ways. It affects the nature of God, as well as of extension and thought. It presents him to us, not as a supernatural being, but as the unity of thought and extension. In knowing these as they are, we know God as he is. Spinoza, in other words, uses the conception of God in a different way from the Cartesians. The latter had treated him as the God of theology,—a being supernatural; Spinoza uses the conception as a scientific one, and speaks of Deus sive Natura.
Leibniz recognized the unphilosophic character of the recourse to a deus ex machina as clearly as Spinoza, and yet did not accept his solution. To find out why he did not is the problem of the historian of thought. The one cause which stands out above all others is that in the unity of Spinoza all difference, all distinction, is lost. All particular existences, whether things or persons, are modes of extension and thought. Their apparent existence is due to the imagination, which is the source of belief in particular things. When considered as they really are,—that is, by the understanding,—they vanish. The one substance, with its two unchanging attributes of thought and extension, alone remains. If it is a philosophic error to give a solution which permits of no unity, is it not equally a philosophic error to give one which denies difference? So it seemed to Leibniz. The problem is to reconcile difference in unity, not to swallow up difference in a blank oneness,—to reconcile the individual with the universe, not to absorb him.
The unsatisfactoriness of the solution appears if we look at it from another side. Difference implies change, while a unity in which all variety is lost implies quiescence. Change is as much an illusion of imagination to Spinoza as is variety. The One Reality is permanent. How repugnant the conception of a static universe was to Leibniz we have already learned. Spinoza fails to satisfy Leibniz, therefore, because he does not allow the conceptions of individuality and of activity. He presents a unity in which all distinction of individuals is lost, and in which there is no room for change. But Spinoza certainly presented the problem more clearly to Leibniz, and revealed more definitely the conditions of its solution. The search is henceforth for a unity which shall avoid the irresolvable dualism of Descartes, and yet shall allow free play to the principles of individuality and of activity. There must be, in short, a universe to which the individual bears a real yet independent relation. What is this unity? The answer, in the phraseology of Leibniz, is the monad. Spinoza would be right, said Leibniz, were it not for the existence of monads. I know there are some who have done Leibniz the honor of supposing that this is his way of saying, “Spinoza is wrong because I am right;” but I cannot help thinking that the saying has a somewhat deeper meaning. What, then, is the nature of the monad? The answer to this question takes us back to the point where the discussion of the question was left at the end of chapter second. The nature of the monad is life. The monad is the spiritual activity which lives in absolute harmony with an infinite number of other monads.
Let us first consider the reasons of Leibniz for conceiving the principle of unity as spiritual. Primarily it is because it is impossible to conceive of a unity which is material. In the sensible world there is no unity. There are, indeed, aggregations, collections, which seem like unities; but the very fact that these are aggregations shows that the unity is factitious. It is the very nature of matter to be infinitely divisible: to say this is to deny the existence of any true principle of unity. The world of nature is the world of space and time; and where in space or time shall we find a unity where we may rest? Every point in space, every moment in time, points beyond itself. It refers to a totality of which it is but a part, or, rather, a limitation. If we add resistance, we are not better situated. We have to think of something which resists; and to this something we must attribute extension,—that is to say, difference, plurality. Nor can we find any resistance which is absolute and final. There may be a body which is undivided, and which resists all energy now acting upon it; but we cannot frame an intelligible idea of a body which is absolutely indivisible. To do so is to think of a body out of all relation to existing forces, something absolutely isolated; while the forces of nature are always relative to one another. That which resists does so in comparison with some opposing energy. The absolutely indivisible, on the other hand, would be that which could not be brought into comparison with other forces; it would not have any of the attributes of force as we know it. In a word, whatever exists in nature is relative in space, in time, and in qualities to all else. It is made what it is by virtue of the totality of its relations to the universe; it has no ultimate principle of self-subsistent unity in it.
Nor do we fare better if we attempt to find unity in the world of nature as a whole. Nature has its existence as a whole in space and time. Indeed, it is only a way of expressing the totality of phenomena of space and time. It is a mere aggregate, a collection. Its very essence
