the sense that they are immediately discovered as separate principles by some one power of the soul called “conscience.” Moral laws are intuitive, he says, “as the consequences of our own development and our true well-being.” Here we may well leave the matter. What is to be said in detail of Leibniz’s ethics will find its congenial home in what we have to say of his theology.
Chapter VII.
Matter and its Relation to Spirit.
Locke’s account of innate ideas and of sensation is only preparatory to a discussion of the ideas got by sensation. His explanation of the mode of knowledge leads up to an explanation of the things known. He remains true to his fundamental idea that before we come to conclusions about any matters we must “examine our own ability.” He deals first with ideas got by the senses, whether by some one or by their conjoint action. Of these the ideas of solidity, of extension, and of duration are of most concern to us. They form as near an approach to a general philosophy of nature as may be found anywhere in Locke. They are, too, the germ from which grew the ideas of matter, of space, and of time, which, however more comprehensive in scope and more amply worked out in detail, characterize succeeding British thought, and which are reproduced to-day by Mr. Spencer.
“The idea of solidity we receive by our touch.” “The ideas we get by more than one sense are of space or extension, figure, rest, and motion.” These sentences contain the brief statement of the chief contention of the sensational school. Locke certainly was not conscious when he wrote them that they were the expression of ideas which should resolve the world of matter and of space into a dissolving series of accidentally associated sensations; but such was none the less the case. When he writes, “If any one asks me what solidity is, I send him to his senses to inform him,” he is preparing the way for Berkeley, and for a denial of all reality beyond the feelings of the individual mind. When he says that “we get the idea of space both by sight and touch,” this statement, although appearing truistic, is none the less the source of the contention of Hume that even geometry contains no necessary or universal elements, but is an account of sensible appearances, relative, as are all matters of sensation.
Locke’s ideas may be synopsized as follows: It is a sufficient account of solidity to say that it is got by touch and that it arises from the resistance found in bodies to the entrance of any other body. “It is that which hinders the approach of two bodies when they are moved towards one another.” If not identical with matter, it is at all events its most essential property. “This of all others seems the idea most intimately connected with and essential to body, so as nowhere else to be found or imagined, but only in matter.” It is, moreover, the source of the other properties of matter. “Upon the solidity of bodies depend their mutual impulse, resistance, and protrusion.” Solidity, again, “is so inseparable an idea from body that upon that depends its filling of space, its contact, impulse, and communication of motion upon impulse.” It is to be distinguished, therefore, from hardness, for hardness is relative and derived, various bodies having various degrees of it; while solidity consists in utter exclusion of other bodies from the space possessed by any one, so that the hardest body has no more solidity than the softest.
The close connection between solidity and matter makes it not only possible, but necessary, to distinguish between matter and extension as against the Cartesians, who had identified them. In particular Locke notes three differences between these notions. Extension includes neither solidity nor resistance; its parts are inseparable from one another both really and mentally, and are immovable; while matter has solidity, its parts are mutually separable, and may be moved in space. From this distinction between space and matter it follows, according to Locke, that there is such a thing as a vacuum, or that space is not necessarily a plenum of matter. Matter is that which fills space; but it is entirely indifferent to space whether or not it is filled. Space is occupied by matter, but there is no essential relation between them. Solidity is the essence of matter; emptiness is the characteristic of space. “The idea of space is as distinct from that of solidity as it is from that of scarlet color. It is true, solidity cannot exist without extension, neither can scarlet color exist without extension; but this hinders not that they are distinct ideas.”
Thus there is fixed for us the idea of space as well as of matter. It is a distinct idea; that is, absolute or independent in itself, having no intrinsic connection with phenomena in space. Yet it is got through the senses. How that can be a matter of sensation which is not only not material, but has no connection in itself with matter, Locke does not explain. He thinks it sufficient to say that we see distance between bodies of different color just as plainly as we see the colors. Space is, therefore, a purely immediate idea, containing no more organic relation to intelligence than it has to objects. We get the notion of time as we do that of space, excepting that it is the observation of internal states and not of external objects which furnishes the material of the idea. Time has two elements,—succession and duration. “Observing what passes in the mind, how of our ideas there in train some constantly vanish, and others begin to appear, we come by the idea of succession, and by observing a distance in the parts of this succession we get the idea of duration.” Whether, however, time is something essentially empty, having no relation to the events which fill it, as space is essentially empty, without necessary connection with the objects which fill it, is a question Locke does not consider. In fact, the gist of his ideas upon this point is as follows: there is actually an objective space or pure emptiness; employing our senses, we get the idea of this space. There is actually an objective time; employing reflection, we perceive it. There is not the slightest attempt to form a philosophy of them, or to show their function in the construction of an intelligible world, except in the one point of the absolute independence of matter and space.
It cannot be said that Leibniz criticises the minor points of Locke in such a way as to throw much light upon them, or that he very fully expresses his own ideas about them. He contents himself with declaring that while the senses may give instances of space, time, and matter, and may suggest to intelligence the stimuli upon which intelligence realizes these notions from itself, they cannot be the source of these notions themselves; finding the evidence of this in the sciences of geometry, arithmetic, and pure physics. For these sciences deal with the notions of space, time, and matter, giving necessary and demonstrative ideas concerning them, which the senses can never legitimate. He further denies the supposed absoluteness or independence of space, matter, and motion. Admitting, indeed, the distinction between extension and matter, he denies that this distinction suffices to prove the existence, or even the possibility, of a vacuum, and ends with a general reference to his doctrine of pre-established harmony, as serving to explain these matters more fully and more accurately.
Leibniz has, however, a complete philosophy of nature. In his other writing, he explains the ideas of matter and force in their dependence upon his metaphysic, or doctrine of spiritual entelechies. The task does not at first sight appear an easy one. The reality, according to Leibniz, is purely spiritual, does not exist in space nor time, and is a principle of activity following its own law,—that of reflecting the universe of spiritual relations. How from this world of ideal, unextended, and non-temporal dynamic realities we are to pass over to a material world of extension, with its static existence in space, and transitory passage in time, is a question challenging the whole Leibnizian system. It is a question, however, for which Leibniz himself has provided an answer. We may not regard it as adequate; we may think that he has not truly derived the material world from his spiritual principles: but at all events he asked himself the question, and gave an answer. We shall investigate this answer by arranging what Leibniz has said under the heads of: matter as a metaphysical principle; matter as a physical phenomenon; and the relation of phenomena to absolute reality, or of the physical to the metaphysical. In connection with the second head, particularly, we shall find it necessary to discuss what Leibniz has said about space, time, and motion.
Wolff, who put the ideas of Leibniz into systematic shape, did it at the expense of almost all their significance. He took away the air of paradox, of remoteness, that characterized Leibniz’s thought, and gave it a popular form. But its depth and suggestiveness vanished