of thought as a communication of vibrations having their seat in the grey substance of the brain.1 The initial movement can transmit itself from one cell to another in every possible direction; hence the variety of associations. Thus, then, without pronouncing upon the value of Hartley's hypothesis, we may say that the scientific theories which have been professed for a century are far from being unfavourable to him.

II.

Now let us approach the psychological study, with which we are more directly concerned.

We have seen that the impression of exterior objects causes vibrations, by means of the ether, which produce sensation. Now, 'sensory vibrations, by being often repeated, beget in the medullary substance of the brain a disposition to diminutive vibrations, which may also be called vibratiuncles, or miniature vibrations, corresponding to themselves respectively.' These vibratiuncles, which are vestiges of the primitive vibration, may be called 'simple ideas of sensation.' The vibratiuncles then produce Ideas.

Hitherto we have explained only the simple elements of thought; we must now enter upon its conditions and complex operations. Here comes in the law of Association.

'Any associations, A, B, C, etc., by being associated with one another a sufficient number of times, get such a power over the corresponding ideas, A, B, C, etc., that any one of the sensations A, when impressed alone, shall be able to excite in the mind B, C, etc., the ideas of the rest.' (Prop. x.)

'Any vibrations, A, B, C, etc., by being associated together a sufficient number of times, get such a power over a, b, c, etc., the corresponding miniature vibrations, that any of the vibrations A, when impressed alone, shall be able to excite b, c, etc., the miniature of the rest. (Prop. XI.)

Thus, then, it is by means of association that simple ideas merge into complex ideas, and concur in their composition.

1 Luys, Recherches sur le Système nerveux, cérébro-spinal, Paris, 1865.

After having explained man as a thinking and feeling being, he remains to be explained as an active being,-that is to say, capable of movement. Here also everything reverts to vibrations, vibra

tiuncles, and association.

In the first place, 'That propensity to alienate construction and relaxation which is observed in almost all the muscles of the body, admits of a solution from the doctrine of vibrations;' the 'motory vibrations,' which contract the muscles, account for automatic movements.

If we admit that the motory vibrations leave vibratiuncles after them, exactly as sensory vibrations do, we may, by the aid of these motory vibrations explain voluntary and semi-voluntary movements. They are rendered possible by an association of the primitive motory vibrations. Hence the whole doctrine of association may be confirmed in the following theorem

'If any sensation A, idea B, or muscular motion C, be associated for a sufficient number of times with any other sensation D, idea E, or muscular motion F, it will at last excite d, the idea belonging to the sensation D, the very idea E, or the very muscular motion F.' (Prop. xx.)

We can now arrive at a collective view of the entire doctrine, and see how all is explained by two things only, vibrations and association.

To simple vibration corresponds sensation.

To associated vibrations complex sensations.

To the vibratiuncle, the simple idea.

To associated vibratiuncles, complex ideas.

To the motory vibrations automatic movement.

To motory vibratiuncles, voluntary and semi-voluntary

movements.

Such are the general laws which, according to Hartley, regulate and explain all the mechanism of the human mind. It only remains for us now to say how he explains the various faculties, senses, memory, imagination, understanding, affections, and will, by attaching them to the law of association.

1. There is no occasion for us to linger over his analyses of the senses. He distinguishes the general sense or feeling, which

is nothing but touch, from the four special senses, and applies himself to explain all by vibrations and associations.

2. Memory is that faculty by which traces of sensations and ideas come, or are recalled, in the same order and proportion, accurately or nearly as they were once presented. The relations between memory and the association of ideas are so evident, so universally recognised, that it is useless to dwell upon them.

3. It is the same with regard to the imagination. When ideas and trains of ideas occur, or are called up in a vivid manner, and without regard to the order of former actual impressions and perceptions, this is said to be done by the power of fancy.' Odd and extravagant associations explain reverie, dreaming, mental alienation, and all their cognate phenomena.

4. The understanding is that faculty by which we contemplate mere sensations and ideas, pursue truth, and assent to or dissent from propositions.' This faculty, in all its essentials, reduces itself to judgment, and, as Hartley says, to proposition, and leads itself back to an association of ideas.

Propositions (affirmative and negative) are of two kinds, rational and practical.

The former are those who have for their object mathematical truths now, in this case, what is the process followed when I say 2 X 2=4, or 12X12=144? My rational assent to the proposition may be defined as a readiness to affirm it to be true, proceeding from a close association of the ideas suggested by the proposition, with the idea or internal feeling belonging to the word truth.

The latter are those which have for their object natural bodies. Hartley's thought may be differently expressed, by saying that the objects of the one are abstracts, and the objects of the other are concretes. The former consist in associating a sensation or a group of sensations given by experience to another sensation, or group of sensations, equally given by experience. For instance: gold is ductile, or soluble in aqua regia. As we see, then, the fundamental operations by which we find scientific or vulgar truths, are brought back by final analysis to associations, to the fusion of simple elements.

5. Hartley afterwards shows how the passions, i.e. the moral

life of man, have their point of departure also in an association of ideas. They set out from two fundamental phenomena-pleasure and pain. But complex sentiments proceed from these simple conditions, by fusion and association.

The passions result from certain sentiments, certain emotions which have been once or several times united to ideas or to circumstances which have the power to reawaken them by the very principle of association.

Let us take fear, for example. We may observe any day that a child is not afraid of a thing except from the moment that that thing has been made to him the real or apparent cause of suffering or punishment. He is not afraid of fire until he has been burned; or of a dog, until the dog has bitten him. In the same way, the passion of love is born of the association of agreeable circumstances with the idea of the object which produces this love.

Our passions may also be all reduced to the sentiments of fear or of affection, varying according to the relation which subsists between their objects and ourselves. In its origin, every passion is always interested, that is to say, it is engendered by an association of ideas founded on pain and on pleasure. But, in consequence of our associations, our passions, in becoming more complex, assume a disinterested character. It is thus that the child loves his mother or his nurse. The idea of that passion associates itself with the various pleasures which she has caused him, which he has experienced in her presence.

Hartley classifies our passions in rather an arbitrary way, which is also a little confused, under the following titles :

The pleasure and pain of imagination, of ambition, of selfinterest, of sympathy, of theopathy, of moral sense.

When he discusses the instincts, he is weak. He shows, however, that they lead back to association. Their point of departure is automatic; the muscles have at first been contracted involuntarily, then this involuntary action has associated itself with the cerebral disturbance which has accompanied it; in other words, the idea unites itself to motion, and motion follows it immediately and mechanically.

6. A mechanism so strict as Hartley's leaves no place for

free-will, and he is too rigid a logician to permit it to enter by an inconsequence. Thus, in the ordinary sense of the word, he absolutely rejects it.

Free-will, he says, may be understood in one of the two following senses :—1. A power of doing either the action A, or its contrary a, while the previous circumstances remain the same. 2. A power of beginning motion. Both one and the other of these two senses are perfectly incompatible with the hypothesis of the mechanism of the mind.

But, if by free-will be meant anything different from these two definitions of it, it may not perhaps be inconsistent with the mechanism of the mind here laid down. Thus, if free-will be defined as the power of doing what a person desires or wills to do, of deliberating, suspending, choosing, or of resisting the motives of sensuality, ambition, resentment, free-will, within certain limitations, is not only consistent with the doctrine of mechanism, but even flows from it; since it appears from the foregoing theory, that voluntary and semi-voluntary powers of calling up ideas, of exciting and restraining affections, and of performing and suspending actions, arise from the mechanism of our nature. This may be called free-will in the popular and practical sense, in contradistinction to that which is opposed to mechanism, and which may be called free-will in a philosophical sense.'

Hartley even maintains that the hypothesis of free-will, reducing itself to the admission of effects without causes, ruins thereby the principle of causality, and consequently, the existence 'of the First Cause.' This constitutes the second portion of his book, into which we shall not follow him.

We do not wish to dwell here upon a philosopher who is interesting, only because he was the first of a school which has gone far beyond him.

His merit consists in two principles. He has clearly perceived that all the operations of the mind are reducible on final analysis to the law of association. He has said this very plainly, and he has tried to demonstrate it. Before him, nothing comparable was to be found in Locke, or even in Hobbes. He has perceived that the question of the relations between the physical and the