confess that physiology is far from being in a position to say precisely to what mode of nerve-vibration a given mode of thought answers. Yet we think that there is one fact which settles the question that we cannot think without words. To think is to form a judgment; to judge is to abstract or generalize, and these operations cannot be performed without signs. The sign is a kind of image-the substitute for an image—and it depends on the brain, as is proved in aphasia, and all disorders of the memory which prevent our using signs. The most abstract reflections, therefore, in so far as they are connected with signs, presuppose a corresponding cerebral state.1

In support of these general considerations, which are based on experience, we may cite, as in the case of the sentiments, some curious facts.

Thus Dr. Dumont, a physician of the Hospital des QuinzeVingts, has inquired into the influence of blindness on the intellectual faculties. Of two hundred and twenty blind persons with whose lives he was perfectly familiar, twenty-seven showed intellectual disorders-not including among these those affected with any appreciable cerebral lesion.

Dr. Renaudin has observed the highly instructive case of an intermittent cutaneous anesthesia that influenced the character

and the intellect of the patient. A youth, Arthur had always given perfect satisfaction to his parents. Gifted with ordinary understanding, he had begun his elementary studies with some success. Suddenly his faculties lost their energy, and he became so unruly that he was expelled the school. He might have been considered an ordinary bad boy,' says M. Renaudin, 'but as I continued my investigation I found in him a complete insensibility of the skin, and I concluded that this was the pathological explanation of the fact. Nor was I mistaken, Arthur has since been sent to Maréville, and from direct observation I have become still more confirmed in this opinion, because the cutaneous anesthesia being somewhat intermittent, it has been

1 We can think without language, but not without some mode or other of physical expression. The famous Laura Bridgman was always moving her fingers in her dreams and during her waking reflections.—(Maudsley, p. 417.)

easier to appreciate its influence on the mind of the patient; when it ceases, he is docile and affectionate. When it reappears, his evil instincts return, and we have had reason to know that they might have led him even to murder.'

It has been observed that when there is perfect physical similarity between twins, which is not rare, it is always accompanied with moral similarity. Moreau saw at Bicêtre two young men who were so much alike that one would be taken for the other. They both possess the same monomania, the same dominant ideas, the same hallucinations of hearing; they never speak to any one, nor do they communicate with one another. 'An exceedingly curious fact, often observed by the attendants and by myself, is this: from time to time, at irregular intervals of two, three, or more months, without appreciable cause, and by the entirely spontaneous action of their malady, a very marked change occurs in both brothers at the same period; often on the same day they quit their habitual state of stupor and prostration and earnestly entreat the physician to give them their freedom. I have seen this repeated even when the two brothers were separated from one another by a distance of several miles.' 1

The phenomenon of suggestion also, as produced in magnetized subjects, and in the state of catalepsy or hypnotism, supplies decisive facts in support of our proposition. Ordinarily, the ideas, sentiments, and volitions suggest the sign, and are interpreted by it; here, on the contrary, the sign suggests the idea, the sentiment, the volition. The phenomenon is reversed. Thus, by placing the magnetized person on his knees, the thoughts of humility and reverence are suggested; by lifting up his lips and his eyelids in a certain way, he is rendered proud and haughty; by raising his arms into the air, or clasping his hands on some object, he is made to think that he is climbing. Carpenter has collected a number of facts of this kind.

It may therefore be said that experience supplies decisive facts. to confirm our proposition, that every psychological phenomenon has a physiological antecedent. It cannot be asserted on sound logical grounds that this is certain. To make it so, the proposition

1 Op. cit., p. 172. See an analogous fact in Trousseau, Clinique Médicale,

i. 253.

should either be strictly deduced from some unquestionable biological law, or else it would have to be possible to give experimental proof of it in all possible cases. We can do neither of these things. But we hold that this thesis possesses all the probability that accompanies the inductive process; we hold that were our science sufficiently advanced, we could, the state of the brain being given, thence deduce the corresponding thought or sentiment; and, conversely, the sentiment or thought being given, we could deduce the state of the brain. Leibnitz, whose genius was all-penetrating, had a glimpse of this truth at a period when science scarce allowed a suspicion of its existence. 'All that ambition led Cæsar's mind to do is represented also in his body; there is a certain state of the body which answers even to the most abstract reasonings.'

We might have deduced our proposition from what was before said; for if it be admitted that the physical and the moral differ not objectively but subjectively-not in their nature, but as to the mode in which they are known to us; if vital phenomena are on the one hand specially mental, and on the other specially physical, but yet such that each of them, taken in its totality, is ever both physical and mental; then it is plain that every psychological phenomenon supposes a corresponding physiological state. But we have thought it best to establish this truth directly, and by experience, independently of all hypotheses. We need only add that here, as everywhere, our solution is restricted to phenomena,. and has nothing to do with the ultimate reasons of things.

CHAPTER III.

PHYSIOLOGICAL AND PSYCHOLOGICAL HEREDITY.

I.

If we sum up what has been said in the two foregoing chapters, we shall see that in consequence of these researches the problem, What is the cause of psychological heredity? is very much simplified.

In the first place, we endeavoured to show that the general

relations of the physical and the moral may be conceived as a relation of equivalence, so that in the last analysis there exists only one species of phenomena, neither material nor spiritual, but which, from a purely human point of view, we call physiological when we grasp them from without and through the senses, and psychological when we grasp them from within and through the consciousness. As we have remarked, however, this is but an hypothesis, the value of which will be better and better determined in the progress of the sciences; but the fate of which is of no importance for the experimental portion of our thesis.

In the next place, passing from speculation to facts, from metaphysics to biology, we showed, on the ground of experience, that it is extremely probable, if not certain, that every mental state implies a corresponding nervous state, and vice versû; so that, were our science more perfect, we might from the mental state of a being infer the nervous state, and from the nervous state infer the mental state.

If these premisses be accepted, the problem of the cause may be more clearly stated. In fact, all our science consists in apprehending relations between simple phenomena or groups of phenomena. We have here two groups of phenomena, the one physiological and, above all, nervous, the other psychological; from the standpoint of heredity there can only subsist between these one or other of these three relations :

1. A simple relation of simultaneity, physiological and psychological heredity being parallel, though entirely independent of one .another.

2. A relation of causality, psychological heredity being considered as the cause, and physiological heredity as the effect.

3. Another relation of causality, but with physiological heredity as the cause, and psychological heredity as the effect.

We will not stop to examine the first hypothesis, which appears to us to be an artificial question. It rests on the strange notion of two substances, the body and the soul, perfectly distinct, entirely different, and so alien to one another, that it is matter for surprise to find them travelling together and in constant relations with one another. The question might have been put in this form in the seventeenth century, but in the present state of science

it is no longer acceptable; and it would not be rash to assert that the great minds who in that age professed this dualism would now be the first to reject it. We have seen that in our time there is a growing tendency to admit an intimate correlation, a mutual interchange between the two orders of phenomena, so that the difficulty is not to unite but to separate them; and we could not explain why this radical dualism is still so accredited, did we not know that it is yet more difficult to extirpate an old error than to bring a new truth into acceptance.

Without insisting on this hypothesis, which in itself alone includes all the difficulties of both the others, let us proceed to examine them.

1. It might be held that psychological heredity is the cause of physiological heredity. This proposition is evidently the one that is maintained by the idealists and the animists. We are not aware that they have laid it down in precise and explicit form, and this no doubt because they have been very little concerned with the problem of heredity, which is chiefly physiological. And, indeed, it is worthy of remark that while spiritualistic philosophy has been much occupied with the future destiny of the soul, it has bestowed very little thought on its origin. It has always inquired whither we are going, and but seldom whence we come. And yet these two problems are intimately connected, and are both equally mysterious.

Theologians have taken more pains to work out this question. It is one that is closely connected with the foundation whereon Christianity rests, the transmission of original sin. Their opinions are not very harmonious, but are of no importance here. They may be reduced under two heads.

Some have taught that God, the only and the immediate origin of souls, creates, at the instant of conception, a special soul for the body which comes into being.

Others hold that all souls are sprung, like all bodies, from the first man, and that they are propagated in the same way-that is, by generation. This would seem to be the opinion of the majority. Tertullian, St. Jerome, and Luther held it, as also two philosophers, Malebranche and Leibnitz. The latter held it to be the only doctrine wherein philosophy can harmonize with religion.'