That there are such unconscious mental actions is laid down in the strongest terms by Leibnitz, whose doctrine reverses the axiom of Descartes into I am, therefore I think. The existence of unconscious thought is maintained by him in terms we might fairly call audacious, and illustrated by some of the most striking facts bearing upon it. The “insensible perceptions,” he says, are as important in pneumatology [spiritual philosophy] as corpuscles are in physics.—It does not follow, he says again, that, because we do not perceive thought, it does not exist.—Something goes on in the mind which answers to the circulation of the blood and all the internal movements of the viscera.—In one word, it is a great source of error to believe that there is no perception in the mind but those of which it is conscious.
This is surely a sufficiently explicit and peremptory statement of the doctrine, which, under the names of “latent consciousness,” “obscure perceptions,” “the hidden soul,” “unconscious cerebration,” “reflex action of the brain,” has been of late years emerging into general recognition in treatises of psychology and physiology.
His allusion to the circulation of the blood and the movements of the viscera, as illustrating his paradox of thinking without knowing it, shows that he saw the whole analogy of the mysterious intellectual movement with that series of reflex actions so fully described half a century later by Hartley, whose observations, obscured by wrong interpretation of the cerebral structure and an insufficient theory of vibrations which he borrowed from Newton, are yet a remarkable anticipation of many of the ideas of modern physiology, for which credit has been given so liberally to Unzer and Prochaska. Unconscious activity is the rule with the actions most important to life. The lout who lies stretched on the tavern bench, with just mental activity enough to keep his pipe from going out, is the unconscious tenant of a laboratory where such combinations are being constantly made as never Wöhler or Berthelot could put together; where such fabrics are woven, such colours dyed, such problems of mechanism solved, such a commerce carried on with the elements and forces of the outer universe, that the industries of all the factories and trading establishments in the world are mere indolence and awkwardness and unproductiveness compared to the miraculous activities of which his lazy bulk is the unheeding centre. All these unconscious or reflex actions take place by a mechanism never more simply stated than in the words of Hartley, as “vibrations which ascend up the sensory nerves first, and then are detached down the motory nerves, which communicate with these by some common trunk, plexus, [network] or ganglion [knot].” The doctrine of Leibnitz, that the brain may sometimes act without our taking cognizance of it, as the heart commonly does, as many internal organs always do, seems almost to belong to our time. The readers of Hamilton and Mill, of Abercrombie, Laycock and Maudsley, of Sir John Herschel, of Carpenter, of Lecky, of Dallas, will find many variations on the text of Leibnitz, some new illustrations, a new classification and nomenclature of the facts; but the root of the matter is all to be found in his writings.
I will give some instances of work done in the underground workshop of thought—some of them familiar to the readers of the authors just mentioned. We wish to remember something in the course of conversation. No effort of the will can reach it; but we say, “Wait a minute, and it will come to me,” and go on talking. Presently, perhaps some minutes later, the idea we are in search of comes all at once into the mind, delivered like a prepaid bundle, laid at the door of consciousness like a foundling in a basket. How it came there we know not. The mind must have been at work groping and feeling for it in the dark: it cannot have come of itself. Yet, all the while, our consciousness, so far as we are conscious of our consciousness, was busy with other thoughts.
In old persons, there is sometimes a long interval of obscure mental action before the answer to a question is evolved. I remember making an inquiry of an ancient man, whom I met on the road in a waggon with his daughter, about a certain old burial-ground which I was visiting. He seemed to listen attentively; but I got no answer. “Wait half a minute or so,” the daughter said, “and he will tell you.” And sure enough, after a little time he answered me and to the point. The delay here, probably, corresponded to what machinists call “lost time,” or “back lash” in turning an old screw, the thread of which is worn. But, within a fortnight, I examined a young man for his degree in whom I noticed a certain regular interval, and a pretty long one, between every question and its answer. Yet the answer was, in almost every instance, correct, when at last it did come. It was an idiosyncrasy, I found, which his previous instructors had noticed. I do not think the mind knows what it is doing in the interval, in such cases. This latent period, during which the brain is obscurely at work, may, perhaps, belong to mathematicians more than others. Swift said of Sir Isaac Newton that, if one were to ask him a question, “he would revolve it in a circle in his brain, round and round and round” (the narrator here describing a circle on his own fore-head), “before he could produce an answer.”
I have often spoken of the same trait in a distinguished friend of my own, remarkable for his mathematical genius, and compared his sometimes long-deferred answer to a question with half a dozen others stratified over it, to the thawing out of the frozen words as told of by Baron Munchausen and Rabelais, and nobody knows how many others before them.
I was told, within a week, of a business man in Boston, who, having an important question under consideration, had given it up for the time as too much for him. But he was conscious of an action going on in his brain which was so unusual and painful as to excite his apprehensions that he was threatened with palsy, or something of that sort. After some hours of this uneasiness, his perplexity was all at once cleared up by the natural solution of his doubt coming to him—worked out, as he believed, in that obscure and troubled interval.
The cases are numerous where questions have been answered, or problems solved, in dreams, or during unconscious sleep. Two of our most distinguished professors in this institution have had such an experience, as they tell me; and one of them has often assured me that he never dreams. Somnambulism and double-consciousness offer another series of illustrations. Many of my audience remember a murder case, where the accused was successfully defended, on the ground of somnambulism, by one of the most brilliant of American lawyers. In the year 1686 a brother of Lord Culpepper was indicted at the Old Bailey for shooting one of the guards and acquitted on the same ground of somnambulism; that is an unconscious and, therefore, irresponsible state of activity.
A more familiar instance of unconscious action is to be found in what we call “absent” persons—those who, while wide awake, act with an apparent purpose, but without really knowing what they are doing; as in La Bruyère's character, who threw his glass of wine into the backgammon board and swallowed the dice.
There are a vast number of movements which we perform with perfect regularity while we are thinking of something quite different—“automatic actions of the secondary kind,” as Hartley calls them, and of which he gives various examples. The old woman knits; the young woman stitches, or perhaps plays her piano and yet talks away as if nothing but her tongue were busy. Two lovers stroll along side by side, just born into the rosy morning of their new life, prattling the sweet follies worth all the wisdom that years will ever bring them. How much do they think about that wonderful problem of balanced progression which they solve anew at every step?