Leibniz’s conception of the matter is brought out when he says that it is indeed true that we begin with particular experiences rather than with general principles, but that the order of nature is the reverse, for the ground, the basis of the particular truths is in the general; the former being in reality only instances of the latter. General principles, he says, enter into all our thoughts, and form their soul and interconnection. They are as necessary for thought as muscles and tendons are for walking, although we may not be conscious of their existence. This side of the teaching of Leibniz consists, accordingly, in the assertion that “innate” knowledge and knowledge derived from experience are not two kinds of knowledge, but rather two ways of considering it. If we consider it as it comes to us, piecemeal and fragmentary, a succession of particular instances, to be gathered up at a future time into general principles, and stated in a rational form, it is seen as empirical. But, after all, this is only a superficial and external way of looking at it. If we examine into it we shall see that there are contained in these transitory and particular experiences certain truths more general and fundamental, which condition them, and at the same time constitute their meaning.
If we inquire into the propriety of calling these truths “innate,” we find it is because they are native to intelligence, and are not acquisitions which it makes. Indeed, it may be said that they are intelligence, so close and organic is their relation, just as the muscles, the tendons, the skeleton, are the body. Thus it is that Leibniz accepts the statement, Nihil est in intellectu quod non fuerit in sensu, with the addition of the statement nisi ipse intellectus. The doctrine of the existence of innate ideas is thus shown to mean that intelligence exists with a real content which counts for something in the realm of experience. If we take intelligence and examine into its structure and ascertain its modes of expression, we find organically inherent in its activity certain conceptions like unity, power, substance, identity, etc., and these we call “innate.” An idea, in short, is no longer conceived as something existing in the mind or in consciousness; it is an activity of intelligence. An innate idea is a necessary activity of intelligence; that is, such an activity as enters into the framework of all experience.
Leibniz thus succeeds in avoiding two errors into which philosophers whose general aims are much like his have fallen. One is dividing a priori and a posteriori truths from each other by a hard and fixed line, so that we are conceived to have some knowledge which comes wholly from experience, while there is another which comes wholly from reason. According to Leibniz, there is no thought so abstract that it does not have its connection with a sensible experience, or rather its embodiment in it. And, on the other hand, there is no experience so thoroughly sensuous that it does not bear in itself traces of its origin in reason. “All our thoughts come from the depths of the soul,” says Leibniz; there are none that “come” to us from without. The other error is the interpretation of the existence of innate ideas or “intuitions” (as this school generally calls them) in a purely formal sense. They are thus considered as truths contained in and somehow expressed by intelligence, but yet not so connected with it that in knowing them we necessarily know intelligence itself. They are considered rather as arbitrary determinations of truths by a power whose own nature is conceivably foreign to truth, than as so many special developments of an activity which may indifferently be called “intelligence” or “truth.” Leibniz, however, never fails to state that an innate truth is, after all, but one form or aspect of the activity of the mind in knowing.
In this way, by bringing to light a deeper and richer conception of what in reality constitutes an innate idea, Leibniz answers Locke. His reply is indirect; it consists rather in throwing a flood of new light upon the matter discussed, than in a ponderous response and counter-attack. But when Leibniz touches upon the conception of a tabula rasa, of a mind which in itself is a mere blank, but has the capacity for knowing, he assumes the offensive. The idea of a bare capacity, a formal faculty, of power which does not already involve some actual content within itself, he repudiates as a relic of scholasticism. What is the soul, which has nothing until it gets it from without? The doctrine of a vacuum, an emptiness which is real, is always absurd; and it is doubly so when to this vacuum is ascribed powers of feeling and thinking, as Locke does. Accepting for the moment the metaphor of a tabula rasa, Leibniz asks where we shall find a tablet which yet does not have some quality, and which is not a co-operating cause, at least, in whatever effects are produced upon it? The notion of a soul without thought, an empty tablet of the soul, he says, is one of a thousand fictions of philosophers. He compares it with the idea of “space empty of matter, absolute uniformity or homogeneity, perfect spheres of the second element produced by primordial perfect cubes, abstractions pure and simple, to which our ignorance and inattention give birth, but of which reality does not admit.” If Locke admits then (as he does) certain capacities inherent in the soul, he cannot mean the scholastic fiction of bare capacity or mere possibility; he must mean “real possibilities,”—that is, capacities accompanied with some actual tendency, an inclination, a disposition, an aptitude, a preformation which determines our soul in a certain direction, and which makes it necessary that the possibility becomes actual. And this tendency, this actual inclination of intelligence in one way rather than another, so that it is not a matter of indifference to intelligence what it produces, is precisely what constitutes an innate idea. So Leibniz feels certain that at bottom Locke must agree with him in this matter if the latter is really in earnest in rejecting the “faculties” of the scholastics and in wishing for a real explanation of knowledge.
But the argument of Locke rests upon yet another basis. He founds his denial of innate ideas not only upon a static conception of their ready made existence “in” the soul, but also upon an equally mechanical conception of consciousness. “Nothing can be in the mind which is not in consciousness.” This statement appears axiomatic to Locke, and by it he would settle the whole discussion. Regarding it, Leibniz remarks that if Locke has such a prejudice as this, it is not surprising that he rejects innate ideas. But consciousness and mental activity are not thus identical. To go no farther, the mere empirical fact of memory is sufficient to show the falsity of such an idea. Memory reveals that we have an indefinite amount of knowledge of which we are not always conscious. Rather than that knowledge and consciousness are one, it is true that actual consciousness only lays hold of an infinitesimal fraction of knowledge. But Leibniz does not rely upon the fact of memory alone. We must constantly keep in mind that to Leibniz the soul is not a form of being wholly separate from nature, but is the culmination of the system of reality. The reality is everywhere the monad, and the soul is the monad with the power of feeling, remembering, and connecting its ideas. The activities of the monad, those representative changes which sum up and symbolize the universe, do not cease when we reach the soul. They are continued. If the soul has the power of attention, they are potentially conscious. Such as the soul actually attends to, thus giving them relief and making them distinct, are actually conscious. But all of them exist.
Thus it is that Leibniz not only denies the equivalence of soul and consciousness, but asserts that the fundamental error of the psychology of the Cartesians (and here, at least, Locke is a Cartesian) is in identifying