As to the philosophy of evolution, we know that, with regard to the origin of the principles of thought, it consists in linking the experience of present generations to that of generations past; in substituting secular for individual experience—in a word, in filling up by the accumulation of ages on ages the interval existing between particular and contingent facts and the universality of principles. This hypothesis is always at bottom no other than that of the tabula rasa, only it is no longer the individual who is this tabula rasa, since each one has, by heredity, received a pre-formed intelligence. Nevertheless, under pain of contradicting the hypothesis, we are forced to admit that there was a first subject who, prior to the action of the object, must have been this tabula rasa. But here the objections of Leibnitz reappear. What can a pure, abstract, and unmodified subject be? And again, before any meeting of subject with object, we have to admit a pure object having nothing subjective, just as the subject had nothing objective. What shall we affirm of this pure object? Let us divest it if you will of colour, heat, sound; must we not at least conceive it as extended, as existing in time, conceive it, that is, according to the necessary forms that are supposed to be suppressed? For to say that it has been capable of existing without having anything in common with these forms, and that out of this unknown and nameless condition have arisen, by way of transformation, the notions of which we treat, were to admit that something can come out of nothing. We must therefore acknowledge that universal notions do at least exist as germs at the origin of evolution. It is not evolution that has created them, evolution has only developed them, and be they ever so attenuated, they still remain conditions without which nothing can be thought.
Such is the gist of the first part of M. Liard’s book, and we have nothing to add to it but our approbation. We can but admire the skilful analysis with which it begins, and the vigorous discussion accompanying that analysis. The three stages traversed by the experimental philosophy of our days—namely, Positivism, the Associative Philosophy, and that of Evolution—are competently and precisely summed up. The discussion is cogent, solid, and could not be further developed without injury to the unity of the work. No doubt it requires close attention to follow it; but it is lucid and well sustained. Whatever the difficulty metaphysic may encounter in constituting itself a science, and getting recognized as such, it has been established that empiricism is not a tenable position, since it has been found necessary to pass from positivism to association, from association to evolution; while evolution itself still supposed some pre-formation. One thing is certain, intelligence invariably contains a something that does not come from without—namely, intelligence itself.
II.
The criticism of Positivism has taught us that there is no knowledge possible without à priori elements—that is to say, without laws inherent in thought, which impose themselves upon phenomena, so as to constitute veritable knowledge. This is the system of Kant, and thus that system avoids not only empiricism, but scepticism as well, though commonly confounded with it. For without necessary laws phenomena only form an arbitrary succession, entirely dependent upon the organization of the individual; we have no longer anything but individual sensations. In the Kantian philosophy, however, the individual is subjected to laws that are superior to himself; these are the laws of human thought, and even, perhaps, of all thought whatever. These laws impose themselves on each one of us in a necessary and universal manner, and by so doing communicate to phenomena an objective reality in this sense at least, that they are for individuals veritable objects; and thus it is that mathematical truths are objects to the intellect, even supposing they should be nowhere realized in any existence independent of thought.
But are these laws of thought anything else than laws of thought? Do they really attain to objective reality—to things in themselves. Kant has denied that they do, and our author, in following in his steps, agrees, or seems to agree, with the “Kritik” of Kant.
Let us then resolve the fundamental laws of the human intellect into five principal concepts: these are, space and time, forms of sensibility, substance and cause, laws of external experience, and, lastly, the Absolute, the final and supreme condition of all knowledge. Now, according to Kant and our author, these notions, at least the four first, are at the same time necessary as subjective conditions of thought, and contradictory so soon as we seek to realize them outside of thought.
For example, that space and time are found by implication in every internal or external representation, that they are not the result of abstraction and generalization, this has been firmly established by Kant; for the elements from which some have sought to derive them already imply them. But, at the same time, they are only internal conditions, of which the objects are unrealizable outside of ourselves, and the reason of this is given by M. Liard, as follows:—Space and time have three essential characteristics, they are homogeneous, continuous, and unlimited. Now, if we seek to make of space and time things in themselves we may doubtless conceive them as homogeneous and continuous, but not as unlimited, for no actual magnitude is unlimited; all magnitude is expressed in numbers, and numbers are necessarily finite, an infinite number involving a contradiction.
We will not enter into a question here mooted by the author, leading to what Leibnitz calls the labyrinth of the continued (Labyrinthus continui), or of invisibles; we will content ourselves with pointing out that the reason here given is not by any means in conformity with the ideas of Kant—indeed, that it contradicts them. In fact, our author here applies to the two forms of sensibility the objection that Kant raised only about real things and the sensible world. The world, indeed, being composed of parts, can only be conceived as infinite by adding these parts to each other, and by thus supposing the actual reality of an infinite number. But it is not so with space, which, not being composed of parts, is consequently not representable by numbers. “There is only one single space, there is only one single time,” says Kant. The notion of space is therefore not formed by the infinite addition of small portions of space and time. These are unities, not numbers. Hence illimitableness is given with the very intuition. “Space,” says Kant, “is represented as a given infinite magnitude,” als eine gegebene unendliche Quantität. Now, so soon as the infinite is given, instead of being made by a mental addition, it seems to us that the above difficulty vanishes.
Let us pass to the notion of substance and to that of cause. These two notions are necessary to render possible the connection of phenomena in the human mind. Our perceptions are, in fact, diverse; if they were only diverse, and had no unity, there would be no passage from one phenomenon to another; consciousness would arise and disappear with each phenomenon, to arise and die anew with the next, and so on. But then there would be no thought, for in order that thought should exist there must be at least two different things presented to the unity of consciousness. In other terms, we should be incapable of perceiving a changing thing without something that was changeless. Hence this is a necessary condition of knowledge. Now, let us see whether this condition can be rendered objective. According to our author it cannot, for if we subtract from surrounding things all the phenomena that fall under the domain of the senses, what remains? Nothing. Common-sense, indeed, believes in substance, but does not mean thereby an abstract and metaphysical entity, it means the whole of what strikes the senses; when the phenomenon is opposed to substance nothing is meant but that a new phenomenon has just added itself to preceding ones. Wood burns; here wood is the substance, combustion the phenomenon. This is how common-sense understands the matter; but if we separate from the idea of wood all that characterizes it as wood, nothing remains but a pure abstraction, of which common-sense takes no account, and has never so much as thought. Our author further combats the idea of substance by appealing to the metaphysical difficulties that it suggests. Is there only one substance, or are there several? Either hypothesis is equally difficult to sustain. In other words, substance is nothing more than that law in virtue of which the mind connects phenomena in one and the same act of thought.
Here, again, we are obliged to say that the preceding arguments against the objectivity of the notion of substance are, in our opinion, far from conclusive. In the first place, it seems to us a false philosophical method to exclude an object from the human mind because it suggests difficulties that we are incapable of solving. Every object must be presented to us as existing before we can judge of the possibility of that object. Perhaps we do not possess the means of solving all the questions which the existence of an object may suggest, but this is no reason why it should not exist. The existence of things cannot be subordinated to the limits of our understanding; it is this very principle which seems to us soundest of all in the “Kritik” of Kant. Even should we be for ever incapable of knowing whether there is one substance or whether there are many, even should we be for ever doomed to doubt as to this point, it would not follow that the existence of one or of many substances were thereby done away with. Moreover, the criticism of our author goes much further than the imperilling the objectivity of substance; it really bears against the very notion itself. If, in fact, every phenomenon being withdrawn, nothing remains any longer in my mind, it is not merely objective substance that vanishes, it is the notion itself. What, indeed, is a notion which, analyzed, comes to naught? And what is this necessary law which is a nonentity? Our author tells us that if we remove all the accidents there remains “nothing perceptible to the senses.” This is mere tautology, for it is too evident that nothing sensible ought to remain in the notion, all sensible accidents having been withdrawn; but what does remain is that without which phenomena could not be connected. And this is no empty concept, for how should an empty concept have any uniting power? And, lastly, when the author, correcting himself, as we think, says that the notion of substance reduces itself to what he calls a “fundamental phenomenon,” he does nothing but change the word, and in reality reverts to what we call substance. For in what sense does anything fundamental—that is to say, that to which other phenomena ultimately reduce themselves, and which cannot be reduced to any other—still preserve the name of phenomenon? All this, therefore, is but admitting under one name what has been denied under another.