balls, as Hobbes; nor of nervous or animal spirits, where inanimate and irrational solids are thawed down, and distilled, or filtrated by ascension, into living and intelligent fluids, that etch and re-etch engravings on the brain, as the followers of Des Cartes, and the humoral pathologists in general; nor of an oscillating ether which was to effect the same service for the nerves of the brain considered as solid fibres, as the animal spirits perform for them under the notion of hollow tubes, as Hartley teaches — nor finally, (with yet more recent dreamers) of chemical compositions by elective affinity, or of an electric light at once the immediate object and the ultimate organ of inward vision, which rises to the brain like an Aurora Borealis, and there, disporting in various shapes, — as the balance of plus and minus, or negative and positive, is destroyed or reestablished, — images out both past and present. Aristotle delivers a just theory without pretending to an hypothesis; or in other words a comprehensive survey of the different facts, and of their relations to each other without supposition, that is, a fact placed under a number of facts, as their common support and explanation; though in the majority of instances these hypotheses or suppositions better deserve the name of upopoiaeseis, or suffictions. He uses indeed the word kinaeseis, to express what we call representations or ideas, but he carefully distinguishes them from material motion, designating the latter always by annexing the words en topo, or kata topon. On the contrary, in his treatise De Anima, he excludes place and motion from all the operations of thought, whether representations or volitions, as attributes utterly and absurdly heterogeneous.
The general law of association, or, more accurately, the common condition under which all exciting causes act, and in which they may be generalized, according to Aristotle is this. Ideas by having been together acquire a power of recalling each other; or every partial representation awakes the total representation of which it had been a part. In the practical determination of this common principle to particular recollections, he admits five agents or occasioning causes: first, connection in time, whether simultaneous, preceding, or successive; second, vicinity or connection in space; third, interdependence or necessary connection, as cause and effect; fourth, likeness; and fifth, contrast. As an additional solution of the occasional seeming chasms in the continuity of reproduction he proves, that movements or ideas possessing one or the other of these five characters had passed through the mind as intermediate links, sufficiently clear to recall other parts of the same total impressions with which they had coexisted, though not vivid enough to excite that degree of attention which is requisite for distinct recollection, or as we may aptly express it, after consciousness. In association then consists the whole mechanism of the reproduction of impressions, in the Aristotelian Psychology. It is the universal law of the passive fancy and mechanical memory; that which supplies to all other faculties their objects, to all thought the elements of its materials.
In consulting the excellent commentary of St. Thomas Aquinas on the Parva Naturalia of Aristotle, I was struck at once with its close resemblance to Hume’s Essay on Association. The main thoughts were the same in both, the order of the thoughts was the same, and even the illustrations differed only by Hume’s occasional substitution of more modern examples. I mentioned the circumstance to several of my literary acquaintances, who admitted the closeness of the resemblance, and that it seemed too great to be explained by mere coincidence; but they thought it improbable that Hume should have held the pages of the Angelic Doctor worth turning over. But some time after Mr. Payne showed Sir James Mackintosh some odd volumes of St. Thomas Aquinas, partly perhaps from having heard that he had in his Lectures passed a high encomium on this canonized philosopher; but chiefly from the fact, that the volumes had belonged to Mr. Hume, and had here and there marginal marks and notes of reference in his own hand writing. Among these volumes was that which contains the Parva Naturalia, in the old Latin version, swathed and swaddled in the commentary afore mentioned
It remains then for me, first to state wherein Hartley differs from Aristotle; then, to exhibit the grounds of my conviction, that he differed only to err: and next as the result, to show, by what influences of the choice and judgment the associative power becomes either memory or fancy; and, in conclusion, to appropriate the remaining offices of the mind to the reason, and the imagination. With my best efforts to be as perspicuous as the nature of language will permit on such a subject, I earnestly solicit the good wishes and friendly patience of my readers, while I thus go “sounding on my dim and perilous way.”
CHAPTER VI
That Hartley’s system, as far as it differs from that of Aristotle, is neither tenable in theory, nor founded in facts.
Of Hartley’s hypothetical vibrations in his hypothetical oscillating ether of the nerves, which is the first and most obvious distinction between his system and that of Aristotle, I shall say little. This, with all other similar attempts to render that an object of the sight which has no relation to sight, has been already sufficiently exposed by the younger Reimarus, Maasz, and others, as outraging the very axioms of mechanics in a scheme, the merit of which consists in its being mechanical. Whether any other philosophy be possible, but the mechanical; and again, whether the mechanical system can have any claim to be called philosophy; are questions for another place. It is, however, certain, that as long as we deny the former, and affirm the latter, we must bewilder ourselves, whenever we would pierce into the adyta of causation; and all that laborious conjecture can do, is to fill up the gaps of fancy. Under that despotism of the eye (the emancipation from which Pythagoras by his numeral, and Plato by his musical, symbols, and both by geometric discipline, aimed at, as the first propaideuma of the mind) — under this strong sensuous influence, we are restless because invisible things are not the objects of vision; and metaphysical systems, for the most part, become popular, not for their truth, but in proportion as they attribute to causes a susceptibility of being seen, if only our visual organs were sufficiently powerful.
From a hundred possible confutations let one suffice. According to this system the idea or vibration a from the external object A becomes associable with the idea or vibration m from the external object M, because the oscillation a propagated itself so as to reproduce the oscillation m. But the original impression from M was essentially different from the impression A: unless therefore different causes may produce the same effect, the vibration a could never produce the vibration m: and this therefore could never be the means, by which a and m are associated. To understand this, the attentive reader need only be reminded, that the ideas are themselves, in Hartley’s system, nothing more than their appropriate configurative vibrations. It is a mere delusion of the fancy to conceive the pre-existence of the ideas, in any chain of association, as so many differently coloured billiard-balls in contact, so that when an object, the billiard-stick, strikes the first or white ball, the same motion propagates itself through the red, green, blue and black, and sets the whole in motion. No! we must suppose the very same force, which constitutes the white ball, to constitute the red or black; or the idea of a circle to constitute the idea of a triangle; which is impossible.
But it may be said, that by the sensations from the objects A and M, the nerves have acquired a disposition to the vibrations a and m, and therefore a need only be repeated in order to reproduce m. Now we will grant, for a moment, the possibility of such a disposition in a material nerve, which yet seems scarcely less absurd than to say, that a weathercock had acquired a habit of turning to the east, from the wind having been so long in that quarter: for if it be replied, that we must take in the circumstance of life, what then becomes of the mechanical philosophy? And what is the nerve, but the flint which the wag placed in the pot as the first ingredient of his stone broth, requiring only salt, turnips, and mutton, for the remainder! But if we waive this, and presuppose the actual existence of such a disposition; two cases are possible. Either, every idea has its own nerve and correspondent oscillation, or this is not the case. If the latter be the truth, we should gain nothing by these dispositions; for then, every nerve having several dispositions, when the motion of any other nerve is propagated into it, there will be no ground or cause present, why exactly the oscillation m should arise, rather than any other to which it was equally
