The general principle of association as laid down by Hartley is this, that if any given sensation, idea, or motion be for a number of times either accompanied, or immediately followed by any other sensation, idea, or muscular motion, the recurrence of the one will afterwards mechanically give rise to that of the other. By immediately followed I mean closely followed: for suppose A to be associated with B, and B with C, A will not only produce B and C intermediately, but will in time produce C immediately without the intervention of B. A mathematician would perhaps here ask how this can ever be actually proved: for though it seems reasonable to suppose that the influence of A if it extend to B should also go a little farther to the next idea, and join indirectly and secretly with B in producing C, yet as the connection between A and B must be stronger than that between A and C, if in any case the connection between the former become gradually so weakened as to dissolve of itself, the latter must fail of course, and therefore C can never follow A, except when B stands equivocally between them. This question would go upon the supposition, that B and C must always be impressions of exactly the same kind and degree of strength, which is not the case. A, though more remote from C, may yet be more intimately connected with it than with B from several other causes, from the greater strength of the impression, from similarity, &c. (This implies by the bye that the effect of association depends on the conjunction of many circumstances, and principles of action, and is not simply determined by the relation of proximity or remoteness between our ideas with respect to time or place.) Thus if a person has done a number of good actions, which have been observed with pleasure by another, this approbation will be afterwards associated with the idea of the person, and the recollection of the benevolent disposition which gave birth to those actions remains when the particular manner in which it was exerted is forgotten. First, because the feeling is the principal or strongest circumstance. Secondly, the association of our ideas with moral qualities is evidently assisted, and forced into the same general direction by the simplicity and uniform character of our feelings compared with the great variety of things and actions, which makes it impossible to combine such a number of distinct forms under the same general notion.
What I have here stated is I believe the whole extent and compass of the law of association. It has been said that this principle is of itself sufficient to account for all the phenomena of the human mind, and is the foundation of every rule of morality. My design is to shew that both these assertions are absolutely false, or that it is an absurdity, and an express contradiction to suppose that association is either the only mode of operation of the human mind, or that it is the primary and most general principle of thought and action.—But first of all it will be necessary to consider the account which Hartley himself has given of this principle as depending on the mechanical communication of motion from the seat of one idea to that of the next and so on, according to a certain local arrangement of these ideas in the brain, as certainly if thought is carried on in this manner, that is, by means of vibrations, it is difficult to conceive of it’s being produced by any other means than the accidental justling of these one against the other, which is what is meant by association.
There are two or three general observations which will be of use in conducting us through this inquiry. In the first place it appears to me certain that every impression or idea is produced in such a manner as to affect or be perceived by the whole brain at once, or in immediate succession, that is, before the action ceases. For if we suppose a certain degree of resemblance to subsist between two ideas, the perception of the one will always be sure to excite a recollection of the other, if it is at all worth remembering. I mean for instance if a person should in some strange place suddenly see an excellent picture of their dead father or mother, I suppose there can be no doubt but the picture would call up the memory of the person whom it resembled with an instantaneous and irresistible force. Now this could not always happen but on the supposition that the visible impression of the picture was conveyed to every part of the brain, as otherwise it must be a mere accident whether it would ever come in contact with that part of it, where that distinct set of recollections was lodged which it was calculated to excite. It is evident that the force with which the impression of the picture acts upon the mind is subsequent to the recollection of the likeness and not the cause of it, since the picture of any other person would act physically upon my mind in the same manner. It may be worth remarking here that the strength, or habitual or recent recurrence of any idea makes it more easily recollected. I might see a picture of a person whom I had not often seen and whose face did not at all interest me at the time without recollecting whose it was, though the likeness should be never so great. The frequent recurrence of the imitation on the other hand if it has had it’s usual effect renders the recollection of the object less certain or at any rate less vivid every time, till at last what remains of it is entirely lost, and confounded with the imitation.[[89]] Again, it is also certain that the proximity of the parts of an object to one another, or of one object to another object is of itself a sufficient and necessary reason for their recollection in succession or together, in the same order in which they were actually perceived. Unless this were the case, we could never recollect any thing at all, as every object is necessarily composed of parts, and those again of others without end. Now how are we to reconcile this with the first-mentioned inference that thought is uniformly and necessarily communicated to every part of the thinking substance? If thought is produced in such a manner, that the shock is immediately felt in those parts nearest the seat of the individual impression, and is indeed sure to excite thought in them without ever affecting the remote parts of the brain in the same manner, it seems strange that it’s own communication over the whole brain should be so rapid and certain, while the force with which it is sent along (as implied in its confined power of producing other thoughts by simple impulse) is so unequal.
The reader will I hope have the good-nature to pardon some inconsistencies of expression in treating of this subject. In order to disprove the theory which I am combating I must first assume it’s truth, and go on talking of the seats of our ideas, the different parts of the brain, the communication of thought by impulse, &c. till it is clearly shewn that the hypothesis to which all these expressions refer is in reality good for nothing.
Though I do not see my way out of the dilemma here stated, and find I have engaged in an undertaking I am not equal to, I think I have seen enough of the difficulties belonging to it to be able to reject the Hartleian hypothesis as directly incompatible with a fair and comprehensive view of the subject. For, first, it has been shewn above that every idea, or perception is communicated to all the parts of the brain, or to the whole sentient principle, whatever this is supposed to be. Or the same thing might be shewn from the nature of consciousness.[[90]] That there is some faculty of this sort which opens a direct communication between our ideas, so that the same thinking principle is at the same time conscious of different impressions, and of their relations to each other, is what hardly any person who attends in the least to what passes in his own mind and is not determined to reason himself out of his senses will I should think deny. In other words, when any two ideas or parts of an idea (for there is no difference in this respect) as those of two lighted candles, or the top and bottom of the same candle are impressed at the same time on different parts of the brain, before these ideas can be perceived in connection as making parts of a whole, or can be accompanied with a consciousness of each other’s existence, we must suppose them mutually to affect the seats of action belonging to each other, or else to be united in some common principle of thought, the same comparing power being exerted upon both. Without supposing their distinct impressions thus to meet in the same point, it seems a thing impossible to conceive how any comparison can take place between different impressions existing at the same time, or between our past, and present impressions, or ever to explain what is meant by saying, I perceive such and such objects, I remember such and such events, since these different impressions are evidently referred to the same conscious being, which idea of individuality could never have been so much as conceived of if there were no other connection between our ideas than that which arises from the juxtaposition of the particles of matter on which they are severally impressed. The mere juxtaposition of the parts of the thinking substance on which different ideas are impressed will never produce any thing more than the actual juxtaposition of the ideas themselves, unaccompanied by any consciousness of their having this relation to each other: for the mind in this case consisting of nothing more than a succession of material points, each part will be sensible of the corresponding part of any object which is impressed upon it, but can know nothing of the impression which is made on any other part of the same substance, except from it’s reaction on the seat of the first, which is contrary to the supposition. In short, to attempt accounting at all for the nature of consciousness from the proximity of different impressions, or of their fluxional parts to each other in the brain seems no less absurd than it would be to imagine that by placing a number of persons together in a line we should produce in them an immediate consciousness and perfect knowledge of what was passing in each other’s minds. If consciousness is to be deduced at all from the circumstance of place, it must be that different impressions occupy exactly the same place. One place has no identity with another: however thin the partition between one idea and another, the distinction must be as absolute and complete, and must confine each idea as effectually within it’s own bounds in this fantastical mosaic-work of the brain, as if the solid skulls of ten philosophers were interposed between each. There is another consideration to be attended to, which is that sensible impressions appear to be continually made on the same part of the brain in succession:—with respect to those received by the eye, a new set of objects is almost every moment impressed on the whole organ, and consequently transmitted along the nerves to the same receptacle in the brain.[[91]] It follows from this last observation in particular (which is not a speculative refinement but a plain matter of fact) that the sphere occupied by different vibrations is constantly the same, or that the same region of the brain belongs equally to a thousand different impressions, and consequently that the mere circumstance of situation is insufficient to account for that complete distinctness, of which our ideas are capable.
From all these considerations taken together I cannot help inferring the fallacy of the Hartleian doctrine of vibrations, which all along goes on the supposition of the most exact distinction and regular arrangement of the places of our ideas, and which therefore cannot be effectually reconciled with any reasoning that excludes all local distinction from having a share in the mechanical operations of the human mind. For if we suppose the succession of our ideas to be carried on by the communication of the impulse belonging to one idea to the contiguous cell, or dormitory of another idea formerly associated with it, and if we at the same time suppose each idea to occupy a separate cell which is inviolable, and which it has entirely to itself, then undoubtedly the ideas thus called up will follow one another in the same order in which they were originally excited. But if we take away this imaginary allotment of separate parcels of the brain to different ideas and suppose the same substance or principle to be constantly impressed with a succession of different ideas, then there seems to be no assignable reason why a vibratory motion accompanied with thought in passing from one part of the thinking substance to the next should not excite any other idea which had been impressed there, as well as the one with which that particular vibration had been originally associated, or why it should not by one general impulse equally excite them all. It is like supposing that you might tread on a nest of adders twined together, and provoke only one of them to sting you. On the other hand to say that this species of elective affinity is determined in it’s operation by the greater readiness with which the idea of a particular impression recalls the memory of another impression which co-existed with it in a state of sensible excitement is to repeat the fact but not (that I can perceive) in any manner to account for it. Let any one compare this account with the one given by Hartley of his own principle, and he will be able to judge.
But farther, even if it could be shewn that the doctrine of vibrations accounts satisfactorily for the association of the ideas of any one sense, (as those of the sight for example) yet surely the very nature of that principle must cut off every sort of communication between the ideas of different senses, (as those of sight and hearing) which may have been associated in the order of time, but which with respect to actual situation must be farther removed from one another than any ideas of the same sense, at whatever distance of time they may have been severally impressed. If from the top of a long cold barren hill I hear the distant whistle of a thrush which seems to come up from some warm woody shelter beyond the edge of the hill, this sound coming faint over the rocks with a mingled feeling of strangeness and joy, the idea of the place about me, and the imaginary one beyond will all be combined together in such a manner in my mind as to become inseparable. Now the doctrine of vibration appears absolutely to exclude the possibility of the union of all these into one associated idea, because as the whole of that principle is founded on the greater ease and certainty with which one local impression is supposed to pass into the seat of the next, and the greater force with which it acts there than it can do farther off, the idea of a visible object can never run into the notion of a sound, nor vice versâ, these impressions being of course conveyed along different nerves to different and very remote parts of the brain. Perhaps it will be said that all ideas impressed at the same moment of time may be supposed to be assigned to particular compartments of the brain as well as where the external objects are contiguous. To this I should answer that such a supposition does not at all account for what I have said above with respect to consciousness and the association of ideas from similarity, &c. and secondly, this supposition is neither included in Hartley’s theory, nor does it seem to be compatible with it, as there is no other reason on the common material hypothesis for inferring the contiguity of our ideas in the brain than the contiguity of their external objects, and the impression of those objects on corresponding parts of the external sensible organ.
The whole of Hartley’s system is founded on what seems an entirely gratuitous supposition, viz. the imaginary communication of our ideas to particular places in the brain to correspond not only with the relations of external objects, but with the order of time. This supposition can never be reconciled with the inference mentioned above (to go no farther) that thought is communicated to every part of the thinking substance by an immediate and uniform impulse. For though we should suppose that it is communicated in one manner to what may be called it’s primary seat, and in a different manner over the rest of the brain, yet we shall still be as much at a loss as ever to shew a reason why it’s primary action should always excite the associated or contiguous ideas, while it’s indirect or secondary action has no power at all to excite any of the ideas, with the spheres of which it necessarily comes in contact in it’s general diffusion over the whole brain, that is by it’s simple impulse. This is not all. There is another circumstance which must entirely prevent the least use being made of this distinction, which is that associated ideas are not properly such as are contiguous in place, but all such as are connected in point of time, the relation of place not being at all essential in the question, for ideas that have been impressed together are always recollected as parts of the same complex impression, without any regard to the proximity or remoteness of their direct, primary seats in the brain, considered as distinct local impressions. As has been explained above with respect to sounds and visible objects, where the association must evidently arise from what I have called their secondary, or relative actions, or, if you will, their conscious ideas, that is those which are not confined to a particular spot in the circumference of the brain, but affect the general principle of thought, whatever this may be, whether composed of extended, material parts, or indivisible. Now if these secondary or conscious ideas which we may represent as continually posting backwards and forwards like couriers in all directions through all quarters of the brain to meet each other and exchange accounts are in fact the only instruments of association, it is plain that the account given by Hartley of that principle falls to the ground at once, first because that account affords no explanation of any of the associations which take place in the mind, except when there is an immediate communication between the primary seats of the associated ideas; secondly, because these secondary or conscious ideas being spread over the whole brain, or rather being impressed on the same thinking principle cannot have any particular connection with or power to call up one another or the contrary from any circumstances of local distinction, which is thus completely done away.—The doctrine of vibrations supposes the order of place and the order of time to correspond exactly in all combinations of our ideas, and that it is owing to this circumstance entirely that those ideas which have been impressed nearly at the same time have afterwards a power to call up one another from the facility with which they must be supposed to pass from their own primary seats into the contiguous ones of the associated ideas. I have endeavoured to shew on the contrary not only that there is no regular local arrangement of our ideas to correspond exactly with the order in which they cohere together in the mind, but that there appears to be no distinction whatever in this respect, that they all belong absolutely to the same place or internal seat of consciousness, that this want of distinction is an evident fact with respect to the successive impressions which are made on the same parts of the body, and consequently on the same parts of the thinking substance, and that it may be deduced generally from the nature of thought itself, and the associations which arise from similarity, &c. that this principle must be entirely nugatory with respect to the associations of the ideas of different senses, even though it should hold true with respect to those of any one sense,[[92]] lastly that all ideas impressed at the same time acquire a power of exciting one another ever after without any regard to the coincidence of their imaginary seats in the brain (according to the material hypothesis) and that therefore the true account of the principle of association must be derived from the first cause, viz. the coincidence of time, and not from the latter which bears no manner of proportion to the effects produced.
The account indeed which Hartley has in one place given of successive association as distinct from synchronous seems to have no necessary connection with this last-mentioned principle. He says, page 69, ‘If A and B be vibrations impressed successively, then will the latter part of A, viz. that part which remains after the impression of the object ceases, be modified and altered by B, at the same time that it will a little modify and alter it, till at last it be quite overpowered by it, and end in it. It follows therefore that the successive impression of A and B sufficiently repeated will so alter the medullary substance, as that when A is impressed alone, it’s latter part shall not be such as the sole impression of A requires, but lean towards B, and end in C at last. But B will not excite a in a retrograde order, since, by supposition, the latter part of B was not modified and altered by A, but by some other vibration, such as C or D.’ First of all, this account seems to imply that the associated impressions A and B are the only ones made on the mind, and that they extend over the whole medullary substance. In this case when the action of A ceases or grows very weak, we may suppose that the tendency to B will be gradually revived, and at last completely overpower that of A, because these are the only impressions existing in the mind, and it must consequently incline to one or other of them, which would be equally the case, whether they had been impressed together, or not. Otherwise we must suppose the impressions thus made successively to have a distinct local communication with each other, or there is no reason given why A should excite b more than any other vibration impressed on the brain in general, or on the seat of b in particular. We must besides this suppose the vibrations A and B to have a particular line of direction, as well as primary sphere of action in the brain to account for B’s not exciting a in the reverse order, &c. The question is how the impression of different objects at the same time, or in quick succession gives the idea of one of those objects a power to excite the idea of the other, though the object is absent; and it is no answer to this question to say, that A being often repeated in connection with B, when it is afterwards excited, ‘leans towards B, and ends in it.’ Hartley says by way of breaking the difficulty, that the latter part of A is altered and modified by B. This is evident enough while B really acts upon the senses: but why should it be modified by it in the absence of B? This modification of the latter part of A by B is not the intermediate cause of the excitement of b, for b, the representative of B, must be excited, at least imperfectly, before it can modify A (B itself being nothing) and the point is how A, or a excites the movement connected with B and that only, not how, supposing this connection between them to be established, the one gradually passes into the other, and ends in it. I think Hartley constantly mistakes tracing the order of palpable effects, or overt acts of the mind for explaining the causes of the connection between them, which he hardly ever does with a true metaphysical feeling. Even where he is greatest, he is always the physiologist rather than the metaphysician.[[93]]
Perhaps a better way to set about discovering the clue to the principle of association, setting aside all ideas of extension, contiguity, &c. would be by considering the manner in which the same conscious principle may be supposed to adapt itself to, to combine, and as it were reconcile together the actions of different objects impressed on it at once, and to all of which it is forced to attend at the same time; by which means these several impressions thus compelled into agreement, and a kind of mutual understanding one with another afterwards retain a particular tendency or disposition to unite together, that is to say, the mind when thrown back into the same state by the recurrence of any one of these ideas is of course put into the way of admitting or passing more readily to any other of the same set of ideas than to any other ideas of a different set not so blended and harmonized with it. It seems as if the mind was laid open to all the impressions which had been made upon it at any given time, the moment any one of them recalls a state of feeling habitually in unison with the rest. By touching a certain spring, all obstacles are removed, the doors fly open, and the whole gallery is seen at a single glance.—The mind has a capacity to perform any complex action the easier for having performed the same action before. It will consequently have a disposition to perform that action rather than any other, the other circumstances being the same. I imagine that association is to be accounted for on the very same principle as a man’s being able to comprehend or take in a mathematical demonstration the better for going over it a number of times, or to recognise any well-known object, as the figure of a man for instance in the middle of a common, sooner than a stump of a tree, or piece of a rock of twice the size, and of just as remarkable a shape.—In like manner, or at least consistently with this, we may suppose, if one impression is very like another, though not associated with it, that the mind will in that case slide more naturally, will feel less repugnance in passing from the recollection of the one to that of the other, that is from it’s actual state into a state very little different from it than into one of a totally different kind. When any particular idea becomes predominant, the turn which is thus given to the mind must be favourable to the reception or recollection of any other idea, which requires but little alteration in the state of the mind to admit it. A slight turn of the screws on which the tension of the mind depends will set it right to the point required. When the actual state of the mind agrees, or falls in with some previous tendency, the effort which the latent idea makes to pass into a state of excitement must be more powerful than it would be without this co-operation, and where the other circumstances are indifferent must always be effectual. Thus the actual feeling of warmth must have a tendency to call up any old ideas of the same kind: e.g. to-day being a very warm day put me in mind of a walk I took in a hot day last summer. Here however another difficulty occurs: for the very opposition of our feelings as of heat and cold frequently produces a transition in the mind from the one to the other. This may be accounted for in a loose way by supposing, that the struggle between very opposite feelings producing a violent and perturbed state of mind excites attention, and makes the mind more sensible to the shock of the contrary impression to that by which it is preoccupied, as we find that the body is more liable to be affected by any opposite extremes, as of heat and cold, immediately succeeding, and counteracting each other. Be this as it may, all things naturally put us in mind of their contraries, cold of heat, day of night, &c. These three, viz. association, similarity, and contrast I believe include all the general sources of connection between our ideas, for as to that of cause and effect, it seems to be referable (as remarked by Priestley) or at least chiefly so to the first class, that of common association.—I hope no one will think me weak enough to imagine that what I have here stated is even a remote and faint approach to a satisfactory account of the matter. Every attempt of this sort must be light and ineffectual without first ascertaining (if that were possible) the manner in which our ideas are produced, and the nature of consciousness, both of which I am utterly unable to comprehend. I have endeavoured simply to point out what it is that is to be accounted for, the general feeling with which a reflecting man should set out in search of the truth, and the impossibility of ever arriving at it, if at the outset we completely cover over our own feelings with maps of the brain, dry skulls, musical chords, pendulums, and compasses, or think of looking into the bottom of our own minds by means of any other instrument than a sharpened intellect.