When Clarke declares that by the absoluteness of space and time he does not mean that they are themselves substances, but only properties, attributes of substance, Leibniz advances the same arguments in different form. If space were the property of the things that are in space, it would belong now to one substance, now to another, and when empty of all material substance, even to an immaterial substance, perhaps to God. “Truly a strange attribute which is handed about from one thing to another. Substances thus leave their accidents as if they were old clothes, and other substances put them on.” Since these finite spaces are in infinite space, and the latter is an attribute of God, it must be that an attribute of God is composed of parts, some of them empty, some full, some round, some square. So, too, whatever is in time would help make one of the attributes of God. “Truly a strange God,” says Leibniz, “this Deity of parts” (ce Dieu à parties). Clarke’s reply to this was that space and time are attributes of God and of God alone, not of things in space and time,—that, indeed, strictly speaking, there are no parts in space or in time; they are absolutely one. This was virtually to give up the whole matter. It was to deny the existence of finite spaces and times, and to resolve them into an indefinite attribute of God. Such a view, as Leibniz points out, not only is contrary to experience, but affords no aid in determining the actual concrete forms and situations of bodies, and durations and successions of events. The absolute space and time, having no parts, are wholly out of relations to these concrete existences. The latter require, therefore, a space and a time that are relations or orders. Clarke’s hypothesis is, as Leibniz says, wholly without use or function, and requires a theory like that of Leibniz to account for the actually determinate forms of experience. In his last reply Clarke shifts his ground again, and says that space and time are effects of God’s existence; “they are the necessary results of his existence.” “His existence is the cause of space and time.” The death of Leibniz prevented any further reply. It is not hard to imagine, however, that in a general way his reply would have been to ask how space and time are at once attributes essential and necessary to God, as constituting his immensity and eternity, and effects dependent upon his existence. To take this latter position, indeed, seems to abandon the position that they are absolute, and to admit that, like the rest of God’s creation, they are relative and finite.
So much for Leibniz’s polemic. Its meaning is that space and time have significance only with reference to things and events, that they are the intellectual, the ideal side of these objects and occurrences, being the relations which give them order and unity. A space which is not the space of objects, which is not space in and through objects, is an inanity; it is not spirit, it is not matter; it is not a relation of either. It is nothingness magnified to infinity, and then erected into existence. And all for nothing; for it does not enable us to account for a single concrete fact of experience. For this we must have recourse to relations and orders of existence. Space is therefore to be defined as the order which makes it possible for objects to have situation; time as that which makes it possible for events to have dating,—not as if they were actually prior to them, and although nothings in themselves, yet capable of giving concrete determination to things, but as actually the relations themselves, and as ideally necessary for the coherent experience of co-existent objects and of connected events. As Leibniz puts it epigrammatically: “Space is the order of possible constants; time the order of inconstant possibilities.”
We have finished the exposition of the views of Leibniz about matter and material facts. One question, however, remains to be discussed,—a question which Leibniz’s contemporary critics would not allow him to pass over in silence, even had he been so disposed. What is the reality of matter, of motion, of space, and of time? Since they are, as Leibniz says, only phenomena, not absolute realities, what distinguishes them from dreams, from illusions? What distinguishes sensible phenomena from capricious fantasies, and gives them reality?
Leibniz begins his answer by pointing out that the mere fact that bodies are phenomena does not make them unreal. To say that anything is phenomenal is to say that it is sensible; but “the senses make no declaration regarding metaphysical matters” such as truth and reality. The senses, in a word, only inform us that the experiences are there for the senses, that they are sensible. What is the ultimate nature of the sensible or the phenomenal, what is their reality, is a question wholly outside the province of sense. The questions of ultimate nature, of reality, are questions of metaphysics, and hence are to be decided by the reason, not by the senses. And Leibniz goes on to say that the truthfulness of the senses, since it concerns only the sensible, consists in the reciprocal agreement of sensible facts, and in that we are not deceived in reasoning from one to another. An isolated sense-experience could not be said to be either true or false, real or illusory. It would be true that it was experienced, and that is all that could be said about it. But since our experiences are not thus separated, but have a certain order, there arises what we may call sensible reality and illusion. When the order between two facts remains the same “in different times and places and in the experience of different men,” we call these facts real. If, however, our experience cannot be repeated by ourselves or by other men when the same conditions (that is, connections) are present, it is unreal, or false. It is thus “the relation of phenomena which guarantees truth of fact regarding sensible objects.” Constancy, regularity, justify us in ascribing reality; chaotic change and lack of orderly connection are a sign of unreality. Even our dreams have a reality; for they have their connections and place in experience. If we understood their connections we should even be able to explain their apparent lack of connection with the rest of experience. Leibniz thinks that both the Academicians and Sceptics and their opponents erred in attempting to find greater reality in sensible things than that of regular phenomena. Since our observations and judgments upon sensible phenomena are of such a nature that we can predict future phenomena and prepare for them, we have all the reality in them that can be had or asked for. Even if it be granted possible (as it must be on this basis) that, metaphysically speaking, sense-experience is only a connected dream, it yet has a sufficient reality; for we are not deceived in the measures taken with reference to phenomena, provided that we act on the ground of their observed harmonies and relations. Thus while we are obliged to admit that our senses inform us that there are hard, passive, extended, indivisible things, not perfectly continuous and not intellectual in their nature, and we know on metaphysical grounds that this information is not correct, we cannot say that our senses deceive us, for sense makes no statements regarding such matters. It is our reason that errs if it takes the information that the senses give as if it were a declaration of reason itself. Sensible things have all the reality necessary for this range of experience,—practical,—such regularity of co-existence and sequence as allows us to act without being led astray.
But if we regard sense-phenomena not merely in their connection with one another, but in their dependence upon the absolute realities, we have still better justification for their comparative reality. These phenomena are consequences of necessary and eternal truths. One endowed with a perfect knowledge of such truths would be able to deduce, a priori, the phenomena from them. The reality of sensible phenomena thus consists not merely in their connection with one another, but in the fact that they are connected as the laws of the intelligible world require. They follow not only rules of co-existence and sequence; but these rules may be brought under general laws of motion, which in turn may be deduced from geometrical principles. These latter, however, are a priori; they are truths which are grounded in the very intelligence of God. The sensible has its basis in the ideal. To state the same fact in another way, all sensible phenomena occur in time and space; or rather, time and space are the orders, the relations, of phenomena occurring and existing. But, as we have just seen, time and space are ideal. A relation, as Leibniz points out, being neither attribute nor accident, cannot be in the things which it relates, as their possession. In his own words, it cannot be conceived as if it had one leg in one object, the other leg in the other. A relation is not a material bond, running through or cementing objects; it is ideal, existing in the mind. And while it is true that space and time are the relations of objects and events, it is also true that if all objects and events were annihilated, space and time would continue to have their ideal existence in the intelligence of God as the eternal conditions of phenomena. They thus form the links between absolute reality and the reality of sensible existence. The principle of sufficient reason forms another link. It may be recalled that in discussing Leibniz’s theory of volition we found that the will of God in relation to the sensible world is always determined by the choice of the better; that in this consists the controlling reason and regulative principle of all that occurs and exists. Thus for every fact in the sensible world there is connection with “metaphysical,” or absolute, reality, not only through the medium of the intellectual relations of time and space, but through the dynamic intermediary of the divine will acting in accordance with the divine reason. Sensible facts have, then, a reality, but a dependent one. There would be no contradiction involved if they were not what they actually are.
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.
Locke’s account of the way in which we get the idea, and of its nature, is as follows: “All the ideas of all the sensible qualities of a cherry come into my mind by sensation. The ideas of these qualities and actions, or powers, are perceived by the mind to be by themselves inconsistent with existence. They cannot subsist of themselves. Hence the mind perceives their necessary connection with inherence, or with being supported.” Correlative to the idea of being supported is, of course, the idea of the support. But this idea “is not represented to the mind by any clear and distinct idea; the obscure and vague, indistinct idea of thing or something, is all that is left.” Or yet more simply, “Taking notice that a certain number of simple ideas go together, and not imagining how these simple ideas can subsist by themselves, we accustom ourselves to suppose some substratum wherein they do subsist, and from which they do result.” Hence the only idea we have of it is of something which underlies known qualities. It is their “supposed, but unknown, support.”
If we translate these expressions into the ideas of to-day, we see that they are equivalent to the view of the world which is given us by scientific categories when these categories are regarded not merely as scientific, but also as philosophic; that is, capable of interpreting and expressing the ultimate nature of experience. This modern view uses the words “things-in-themselves” (or absolute realities) and “phenomena.” It says that we know nothing of existence as it is in itself, but only of its phenomena. Mind, matter, objects, are all substances, all equally substances, and all have their unknown essence and their phenomenal appearance. Such a distinction between the known and the unknown can rest, it is evident, only upon a separation between reality and phenomena similar to that which Locke makes between substance and qualities. In knowing the latter, we know nothing of the former. Although the latter are called “phenomena,” they do not really manifest the substantial reality; they conceal it. This absolute distinction between substance and quality, between reality and phenomenon, rests, in turn, upon the hypothesis that reality is mere existence; that is, it is something which is, and that is all. It is a substratum; it lies under, in a passive way, qualities; it is (literally) substance; it simply stands, inactively, under phenomena. It may, by possibility, have actions; but it has them. Activities are qualities which, like all qualities, are in external relation to the substance. Being, in other words, is the primary notion, and “being” means something essentially passive and merely enduring, accidentally and secondarily something acting. Here, as elsewhere, Locke is the father of the mechanical philosophy of to-day.