Di Marco Trainito
La Cronologia della Mente
L'attualità di queste due pagine titaniche è impressionante. Le nostre menti occidentali "girano" ancora, in gran parte, seguendo l'uno o l'altro "programma" logico-argomentativo. Quello di Locke è più diffuso, anche perché, stando a certi studi recenti, sembra radicato nella nostra evoluzione cognitiva. E infatti lo si riscontra già in esecuzione nella mente dei bambini. Eppure contiene un errore gigantesco, perché ignora una delle poche cose certe che la nostra conoscenza del mondo ci suggerisce, ovvero che la mente è apparsa da poco sulla scena del gran teatro della natura. Per correggere l'errore di Locke (che in fondo non fa altro che dare veste filosofica all'incipit del vangelo di Giovanni e a ogni intuizione possibile sul cosiddetto "disegno intelligente"), Hume fa tutto quello che era umanamente possibile fare prima di Darwin e dello sviluppo delle neuroscienze.
Locke, "Essay", 1690, IV, X, 10:
“Incogitative being cannot produce a cogitative being. If, then, there must be something eternal, let us see what sort of being it must be. And to that it is very obvious to reason, that it must necessarily be a cogitative being. For it is as impossible to conceive that ever bare incogitative matter should produce a thinking intelligent being, as that nothing should of itself produce matter. Let us suppose any parcel of matter eternal, great or small, we shall find it, in itself, able to produce nothing. For example: let us suppose the matter of the next pebble we meet with eternal, closely united, and the parts firmly at rest together; if there were no other being in the world, must it not eternally remain so, a dead inactive lump? Is it possible to conceive it can add motion to itself, being purely matter, or produce any- thing? Matter, then, by its own strength, cannot pro- duce in itself so much as motion: the motion it has must also be from eternity, or else be produced, and added to matter by some other being more powerful than matter; matter, as is evident, having not power to produce motion in itself. But let us suppose motion eter- nal too: yet matter, incogitative matter and motion, whatever changes it might produce of figure and bulk, could never produce thought: knowledge will still be as far beyond the power of motion and matter to produce, as matter is beyond the power of nothing or nonentity to produce. And I appeal to every one’s own thoughts, whether he cannot as easily conceive matter produced by nothing, as thought to be produced by pure matter, when, before, there was no such thing as thought or an intelligent being existing? Divide matter into as many parts as you will, (which we are apt to imagine a sort of spiritualizing, or making a thinking thing of it,) vary the figure and motion of it as much as you please—a globe, cube, cone, prism, cylinder, &c., whose diameters are but 100,000th part of a gry, will operate no otherwise upon other bodies of proportionable bulk, than those of an inch or foot diameter; and you may as rationally expect to produce sense, thought, and knowledge, by putting together, in a certain figure and motion, gross particles of matter, as by those that are the very minutest that do anywhere exist. They knock, impel, and resist one another, just as the greater do; and that is all they can do. So that, if we will suppose nothing first or eternal, matter can never begin to be: if we suppose bare matter without motion, eternal, motion can never begin to be: if we suppose only matter and motion first, or eternal, thought can never begin to be. For it is impossible to conceive that matter, either with or without motion, could have, originally, in and from itself, sense, perception, and knowledge; as is evident from hence, that then sense, perception, and knowledge, must be a property eternally inseparable from matter and every particle of it. Not to add, that, though our general or specific conception of matter makes us speak of it as one thing, yet really all matter is not one individual thing, neither is there any such thing existing as one material being, or one single body that we know or can conceive. And therefore, if matter were the eternal first cogitative being, there would not be one eternal, infinite, cogitative being, but an infinite number of eternal, finite, cogitative beings, independent one of another, of limited force, and distinct thoughts, which could never produce that order, harmony, and beauty which are to be found in nature. Since, therefore, what- soever is the first eternal being must necessarily be cogitative; and whatsoever is first of all things must necessarily contain in it, and actually have, at least, all the perfections that can ever after exist; nor can it ever give to another any perfection that it hath not either actually in itself, or, at least, in a higher degree; it necessarily follows, that the first eternal being cannot be matter”.
Hume, "Treatise", 1739, I, IV, 5:
“If you pretend, therefore, to prove a priori, that such a position of bodies can never cause thought; because turn it which way you will, it is nothing but a position of bodies; you must by the same course of reasoning conclude, that it can never produce motion; since there is no more apparent connexion in the one case than in the other. But as this latter conclusion is contrary to evident experience, and as it is possible we may have a like experience in the operations of the mind, and may perceive a constant conjunction of thought and motion; you reason too hastily, when from the mere consideration of the ideas, you conclude that it is impossible motion can ever produce thought, or a different position of parts give rise to a different passion or reflection. Nay it is not only possible we may have such an experience, but it is certain we have it; since every one may perceive, that the different dispositions of his body change his thoughts and sentiments. And should it be said, that this depends on the union of soul and body; I would answer, that we must separate the question concerning the “substance of the mind from that concerning the cause of its thought; and that confining ourselves to the latter question we find by the comparing their ideas, that thought and motion are different from each other, and by experience, that they are constantly united; which being all the circumstances, that enter into the idea of cause and effect, when applied to the operations of matter, we may certainly conclude, that motion may be, and actually is, the cause of thought and perception”.