But however complete and concordant may be the actions of our senses, when it is a question of knowing an object—even when, as in sexual love, the six senses, including the genital sense, come into play simultaneously—it is none the less the fact that the object known remains exterior to ourselves. Besides, this qualification "known" is little appropriate to the object perceived, since it has an interior face, inaccessible at first glance to our senses. If we are dealing with a living being—and all the more if this being be intelligent and complex—we must exercise all sorts of faculties and devote ourselves to minute analyses in order to arrive, even then, at a knowledge that is very nearly illusory.
Knowledge arrives, then, at a certain bankruptcy. It is not very far from this point to that of proclaiming the uselessness of the external world as a means of explaining the nature of knowledge itself. It is only a step from uselessness to reality. The idealistic philosophers who develop their theory to its logical conclusion, can say, without paradox, that everything occurs in vision, for example, as if the object did not exist—as if intelligence, though believing that it receives aid from the eye, in reality created this object just as far as it wishes to know it. The phenomenon of hallucinations gives an appearance of reason to these exasperated idealists. Did not Taine, who was not exasperated, call sensation a true hallucination? But why true? That is a word which, in the circumstances, it is difficult to justify. It would be juster to say that hereditary habit inclines us to regard certain sensations as true, certain others as false. Perhaps utility serves us also as guide, and we imagine, in order to reassure ourselves, an external and fallacious world whose operations correspond to the movements of our psychology.
II
There is another way of knowing, at once more elementary, more intimate, and more uncertain. This is absorption. The elements of our nourishment, in proportion as we "know" them, disintegrate, yield soluble parts to our organism, and reject the rest in a form equally unknowable. If we reject, as we should, the primitive distinction between soul and body, admitting only the body and believing everything to be physical, then this way of knowing should be studied parallel with those ways which spring from each of our different senses, or from their collaboration. It is certain that absorption has taught man in every age. It is through it, and not by virtue of an unknown instinct, that he has succeeded in separating vegetables and animals into good and bad, into useful and harmful or indifferent. Our analytical methods are still unable, save perhaps in particularly expert hands, to distinguish mushrooms as a harmful or favourable form of nourishment. The expert himself must be guided, for this delicate operation, by a direct and real experiment of absorption. Man, devoid of science, took himself as laboratory. None was surer. He acquired, by this means, certain parts of his knowledge which have proved most useful to humanity and to the domestic animals. From time to time medications are rediscovered which figure in ancient pharmacopeias. Thus formate of lime or of soda, recently prescribed as a muscular invigorant, contains scarcely a principle that did not figure in the old "water of magnanimity," obtained by maceration and distillation of a certain quantity of ants. How did our ancestors, who were no doubt shepherds and labourers, come to distinguish the virtue of ants? Evidently by eating them. The foul Arabs and other low forms of humanity who eat their vermin, find in them, perhaps, an analogous tonic. This practice, like all those which resolve themselves into absorption, is assuredly dictated by experience. Neither a man nor an animal can, in principle, become addicted to an act which is harmful to him. Between acts that are harmful, and acts that are salutary, there is a whole series of games, but it is difficult to admit that a daily game is a harmful act.
Why do not peasants eat certain abundant rodents? It is easy to answer by offering taste and disgust as pretexts; but this is reversing the logical order of the terms of the argument.
A food does not disgust by its odour. The odour of a food disgusts because this food is harmful or useless. To understand this, without the necessity of insisting upon it, it is enough to think of all those foods with nauseous odours, which we appreciate much more than those which might be considered pleasant. Such is the fruit of experience, that is to say, of knowledge.
I believe that absorption should be considered one of the best means we have of appreciating the practical value of certain parts of the external world. Agriculture, kitchen-gardening, cooking, pharmacy almost entirely, are born of it. Assuredly men, even the rarest chemists and physiologists, could suck a kola-nut for years, without suspecting those virtues that savages found quite simply by cracking it with their teeth.
They jest who, ignoring not only the importance but the very existence of this sixth or seventh or tenth sense, attribute to taste or to smell a mysterious power of divining the harmfulness of a plant or of its fruit. How can they help seeing immediately that this preservative instinct, if it be hereditary, has had a beginning, and that, at this beginning, there was a fact of knowledge? The traditional notion of instinct must be left in the old theological and spiritualistic repertories. It serves simple people as an easy means of distinguishing man from the animals. Animals have instinct, man has intelligence. There are proofs. Man poisons himself with mushrooms, frugivorous animals never. What man? Not the traditional peasant surely. Only the déraciné or the city-dweller, who has naturally lost an instinct which was useless to him. This proof proves only that it is dangerous for man, as for the other animals, or for plaints themselves, to change their habitat. There is a painful, uncertain transitory phase. It is during this phase that we go into the woods, picknicking, and gather toadstools. But rabbits in cages, when given wet grass or vegetables instinctively unknown to them, allow themselves to be completely poisoned. Free, it would never have occurred to them to crop at dewfall, because their ancestors, dwelling in extremely thick woodlands, were ignorant of the very existence of the dew, and transmitted distrust of wet grass to their offspring.
Man, even in the state of semi-civilization, is burdened with too much knowledge for it all to be transmitted hereditarily; but there is no doubt that the oldest and most useful reaches us in this manner. When we walk in the forest there are berries that tempt us, whortleberries, for example, but never alderberries. Who has taught us (I am supposing a real ignorance), that they are purgative and even dangerous? Instinct? What is instinct? The hereditary transmission of knowledge.
This transmission can, without doubt, occur in the case of abstract ideas, as well as of practical ideas—that is to say, useful for the conservation of life. Some, besides, are really useful, and even primordial. It is as reasonable to believe that they are inherited as to suppose them personally acquired. It might be possible to rehabilitate the theory of innate ideas, by revising it carefully and eliminating from its catalogue all sorts of Platonic or Christian inventions, too recent to have entered our blood.