David Hartley

“ It is remarkable here, that the hearts of frogs, vipers, and several other such animals, as can live in great degrees of cold, and without respiration, continue to beat, as has been taken notice of above, for a long time after they are taken out of their bodies. We must therefore suppose, that the fibres of their hearts, and the blood globules which remain in them, are endued with an electric, or other attractive virtue, of a more durable kind than the fibres and blood globules of the more perfect animals ”

“ Now, if it be found, upon a careful and impartial inquiry, that the motions which occur every day in common life, and which follow the idea called the will, immediately or mediately, perfectly or imperfectly, do this, in proportion to the number and degree of strength in the associations, this will be sufficient authority for ascribing all which we call voluntary in actions to association, agreeably to the purport of this proposition. ”

“ Hook’s, in which he kept a dog alive, by a mere continued stream of fresh air passing through the lungs, without any such alternate motion of the chest as takes place in common respiration, that one principal use of the air, which is an electric per se, in respiration, is to restore to the blood, as it passes through the lungs, that electricity which it has lost in circulating through the body? ”

“ VIII. When objects and ideas, with their most common combinations, have been often presented to the mind, a train of them, of a considerable length, may, by once occurring, leave such a trace, as to recur in imagination, and in miniature, in nearly the same order and proportion as in this single occurrence. For, since each of the particular impressions and ideas is familiar, there will want little more for their recurrency, than a few connecting links ”

“ Now, since the human body is composed of the same matter as the external world, it is reasonable to expect, that its component particles should be subjected to the same subtle laws. And the exquisite structure of animal bodies in so many other respects, makes it easier to conceive, that the organ of organs, viz. the medullary substance, should be endued with a proper subtle ultimate structure, for the purpose of retaining a state that is frequently impressed. ”

“ And this seems very probable; for the muscles are hard during contraction, soft during relaxation; and hardness and softness are evidently nothing but variations in the cohesion of the small particles of bodies. Neither is this conjecture at all repugnant to the supposition of an electrical attraction above made, or to the doctrine of vibrations; for electricity may reach to small distances, without being excited by friction, and flow from the same principle as the cohesion of bodies, as Sir Isaac Newton has observed. ”

“ Respiration and crying are excited in the new-born child from the cold handling of the midwife, and other vivid sensations impressed immediately upon its coming into the world. These vivid sensations put the whole system of muscles, or at least those of the trunk and larynx, into action at once, as far as their mutual antagonism will permit, the stronger set of conspiring muscles overpowering the weaker for a certain short time, and then, after their force is exhausted, according to Prop. XVII. giving way for a shorter time to the weaker. ”

“ And as a vibratory motion is more suitable to the nature of sensation than any other species of motion, so does it seem also more suitable to the powers of generating ideas, and raising them by association. However, these powers are evident independently, as just now observed; so that the doctrine of association may be laid down as a certain foundation, and a clew to direct our future inquiries, whatever becomes of that of vibrations. ”

“ Thirdly, That the vibrations thus excited in the fibres, put into action an attractive virtue, perhaps of the electrical kind, which lies concealed in the particles of the fibres, or in the blood-globules, or both. That the blood-globules of animals are electrical, may be conjectured from the electricity of those of the muscle-shell fish, observed by Dr. Hales; and that the red blood has a principal share in muscular contraction is highly probable, from the red colour of all the great muscles of the body, and from the weakness of all young animals, and of such as want a due share of red blood. ”

“ We may also perhaps discover hereafter, from the nature of vibratory motions, and of the human brain, compared with the circumstances of life, why the ideas of one sense are more vivid and distinct than those of another. ”

“ And, therefore, in dreams, where complex associations are much weakened, and various parcels of visible ideas, not joined in nature, start up together in the fancy, contiguous to each other, we often see monsters, chimeras, and combinations, which have never been actually presented.
Association seems also necessary to dispose the medullary substance to this or that miniature vibration, in succession, after the miniatures of a large number of original vibrations have been generated. ”

“ It is very remarkable, that the pale fibres of the intestines, in men, and many other animals, preserve their power of alternate contraction and relaxation for a considerable time after death, whereas the red fleshy muscles of the same animals lose theirs soon after the effusion of their blood. ”

“ The fibres of the relaxed muscle may also be considered as under a state of distention to a certain degree, and, consequently, as liable to an increase of vibrations upon this account. To which we may farther add, that since vibrations are hindered from passing into the contracted muscle, in the manner just now explained, they will pass with greater force into the relaxed one, from the place of the common derivation of their nerves, wherever there are antagonist muscles that derive nerves from the same trunk, as in the limbs, and muscles of respiration. ”

“ And thus, from the present proposition, and the nineteenth taken together, we are enabled to account for all the motions of the human body, upon principles which, though they may be fictitious, are, at least, clear and intelligible. ”

“ Thus, to mention a gross instance, we could have no proper idea of a horse, unless the particular ideas of the head, neck, body, legs, and tail, peculiar to this animal, stuck to each other in the fancy, from frequent joint impression. ”

“ The power of miniature vibrations to raise other miniatures may, perhaps, be made clearer to mathematicians, by hinting, that the efficacy of any vibration to raise any other, is not in the simple ratio of its vividness, but as some power thereof less than unity ”

“ VII. Our original bodily make, and the impressions and associations which affect us in passing through life, are so much alike, and yet not the same, that there must be both a great general resemblance amongst mankind, in respect to their intellectual affections, and also many particular differences. ”

“ Hence we may conceive, that a very complex set of vibrations, arising from the mixture and combinations of degree, kind, place, and line of direction, exists always in the medullary substance, being kept up by its heat, and the pulsation of its arteries, when other causes are wanting, almost in the same manner as in a concert of music the air is agitated by vibrations of a very complex kind. ”

“ It is to be observed, that, in successive associations, the power of raising the ideas is only exerted according to the order in which the association is made. Thus, if the impressions A, B, C, be always made in the order of the alphabet, B impressed alone will not raise a, but c only. Agreeably to which it is easy to repeat familiar sentences in the order in which they always occur, but impossible to do it readily in an inverted one. The reason of this is, that the compound idea, c, b, a, corresponds to the compound sensation C, B, A ”

“ First, then, We are to conceive, that those sensory vibrations which are excited in the external organs, and ascend towards the brain, when they arrive, in their ascent, at the origins of motory nerves, as they arise from the same common trunk, plexus, or ganglion, with the sensory ones affected, detach a part of themselves at each of these origins down the motory nerves; which part, by agitating the small particles of the muscular fibres, in the manner explained in the sixteenth proposition, excites them to contraction. ”

“ For thus we may learn how to cherish and improve good ones, check and root out such as are mischievous and immoral, and how suit our manner of life, in some tolerable measure, to our intellectual and religious wants. ”

“ The yawnings and stretchings of persons disposed to sleep, the convulsive respiration of those that are just fallen asleep, and the convulsive motions which attend the extinction of the senses in epileptic fits, and the near approaches of death, may be derived, perhaps, in part, from this source, in part from some of the foregoing. ”

“ IV. Since God is the source of all good, and consequently must at last appear to be so, i.e. be associated with all our pleasures, it seems to follow, even from this proposition, that the idea of God, and of the ways by which his goodness and happiness are made manifest, must, at last, take place of, and absorb all other ideas, and he himself become, according to the language of the Scriptures, All in all. ”

“ And it is certainly a presumption in its favour, that a less power of generating miniatures will be a foundation for a larger of association, and vice versâ, till, at last, the whole superstructure of ideas and associations observable in human life may, by proceeding upwards according to analysis, and downwards according to synthesis, be built upon as small a foundation as we please. ”

“ IX. When the pleasure or pain attending any sensations and ideas is great, all the associations belonging to them are much accelerated and strengthened. For the violent vibrations excited in such cases, soon overrule the natural vibrations, and leave in the brain a strong tendency to themselves, from a few impressions. ”

“ It is also to be observed, that the power of association grows feebler, as the number either of synchronous or successive impressions is increased, and does not extend, with due force, to more than a small one, in the first and simplest cases. ”

“ And unless we do suppose some such subtle vibrations as these, it will be extremely difficult to conceive, how so soft a pulp as the medullary substance is, should be the common instrument of sensation, thought, and motion; which yet all physicians and philosophers must allow, according to the first and second propositions. ”

“ I will, in the next place, give a short account of the manner in which we learn to speak, as it may be deduced from the foregoing proposition. The new-born child is not able to produce a sound at all, unless the muscles of the trunk and larynx be stimulated thereto by the impression of pain on some part of the body. As the child advances in age, the frequent returns of this action facilitate it ”

“ XII. This proposition, and its corollaries, afford some pleasing presumptions; such are, that we have a power of suiting our frame of mind to our circumstances, of correcting what is amiss, and improving what is right: that our ultimate happiness appears to be of a spiritual, not corporeal nature; and therefore that death, or the shaking off the gross body, may not stop our progress, but rather render us more expedite in the pursuit of our true end: that association tends to make us all ultimately similar ”

“ It is evident from the nature of vibratory motions, that the medullary substance will not, immediately upon the removal of this object, return to its natural state N, but will remain, for a short space of time, in the preternatural state A, and pass gradually from A to N. Suppose the same object to be impressed again and again, for a sufficient number of times, and it seems to follow, that the medullary substance will be longer in passing from A to N, after the second impression than after the first, after the third impression than second, &c. ”

“ By degrees the motions cling to one another, and to the impressions of the notes, in the way of association so often mentioned, the acts of volition growing less and less express all the time, till at last they become evanescent and imperceptible. For an expert performer will play from notes, or ideas laid up in the memory, or from the connexion of the several complex parts of the decomplex motions, some or all ”

“ If those of the right side arise from the left part of the brain, and vice versâ, which seems to be the opinion of the best anatomists, then one would imagine, that the homonymous nerves of the right and left sides must, in crossing over, lie somewhere contiguous to each other, and so impart vibrations to each other. ”

“ II. It seems also, that many very complex propensities and pursuits in adults, by which they seek their own pleasure and happiness, both explicitly and implicitly, may be accounted for, upon the same, or such-like principles. ”