I cannot better explain the modern theory of the understanding (which it will be the object of this letter to consider) than in the words of one of the best and ablest commentators of that school, Mr. Horne Tooke.
‘The business of the mind,’ he says ‘appears to me to be very simple. It extends no farther than to receive impressions, that is, to have sensations or feelings. What are called its operations are merely the operations of language. The greatest part of Mr. Locke’s Essay, that is, all which relates to what he calls the composition, abstraction, complexity, generalization, relation, etc. of ideas, does indeed merely concern language. If he had been sooner aware of the inseparable connection between words and knowledge, he would not have talked of the composition of ideas, but would have seen that the only composition was in the terms, and consequently, that it was as improper to talk of a complex idea as of a complex star! I will venture to say that it is an easy matter, upon Mr. Locke’s own principles and a physical consideration of the senses and the mind, to prove the impossibility of the composition of ideas, and that they are not ideas, but merely terms, which are general and abstract.’—Diversions of Purley, Vol. i. p. 39, 51, &c.[[10]]
Now this is very explicit, and, I also conceive, very logical. For I am ready to grant that ‘Mr. Locke’s own principles and a physical consideration of the mind’ do lead to the conclusions here stated; and it is on that account that I shall attempt to shew that those principles and the consideration of the mind, as a physical thing, are in themselves absurd. These writers taking up the principle, that to have sensations or feelings was the only real faculty of the mind, and perceiving that the having sensations merely was a different thing from having an idea or consciousness of their relations (inasmuch as no sensation as such can include a knowledge of or reference to any other) have inferred very rationally that all the operations of the mind founded on a principle of general consciousness or common understanding, viz. compounding, comparing, discerning, judging, reasoning, etc. were excluded from their physical theory of sensation, and must be referred to some trick or deception of the mind, the mechanism of language or habitual association of ideas. According to this theory, besides the sensible impressions of individual objects, and their distinct traces left in the memory—the rest is merely words. In supposing that we combine these different impressions together, that we compare different objects, that we reason upon them, it seems we only deceive ourselves, and mistake a rapid and mechanical transition from one idea to another for the actual perception of the relations between them. Thus have these philosophers sacrificed all the known facts and conscious operations of the mind to a literal deduction from a gross verbal fallacy. For what are these single objects or individual ideas, of which the senses are competent to take cognizance, and beyond which the understanding can never advance a step? Neither more nor less than complex and general ideas, which imply all the same intellectual impossibilities of comparing, judging, distinguishing, &c. i.e. of perceiving a number of diversified relations, of connecting the MANY into the ONE, which are objected to the more deliberate and formal acts of understanding and reason. The mind, say they, can perceive but one idea at a time, that is, it may perceive a square or a triangle, but it cannot compare them together, or perceive their proportions, because to do this, it must attend to different ideas at once. Yet what is this individual idea of a square, for instance, but an idea of given lines, their direction, equality, connection, &c. all which must be combined together in the mind, before it can possibly form any idea of the object? Mr. Tooke says, the complexity is in the term. I should say, the individuality is in the term, that is, in the application of one name to a collective idea, which superficial reasoners, at once the slaves of idle paradox and vulgar prejudice, have therefore imagined to be one thing. The whole error of this system has, indeed, arisen from considering ideas themselves, or those particular objects, which are marked by a single name, or strike at once, and in a mass, upon the senses, as simple things. But there is no one of these particular ideas, as they are called, which is not an aggregate of many things, or that can subsist for a moment but in the understanding. By destroying the composition of ideas, all ideas as well as all combinations of ideas, would be completely and for ever banished from the mind; which would be left a mere tabula rasa, a blank, indeed, or would at all times strictly resemble what Mr. Locke describes it to be in its original state, ‘a dark closet with a little glimmering of light let in through the loop-holes of the senses.’
Writers, in general, who have maintained the existence of a distinct faculty besides the senses, have applied themselves to shew that, besides particular ideas or objects, it was necessary to admit the understanding to explain the perception of the relations between them. My purpose is to shew that the same perception of relation, the same understanding is implied in the very ideas or objects themselves. To have sensations is not to compare them, that is, sensation and understanding are not the same thing. To have ideas, it is necessary to compare our sensations, that is, ideas and understanding are the same thing.
I can conceive then of a being endued with the power of sensation, so as to receive the direct impressions of outward objects, and also with memory, so as to retain them for any length of time, as they were severally and unconnectedly presented, yet without any signs of understanding. The state of such a being would be that of animal life, and something more (with the addition of memory), but it would not amount to intellect. As this distinction is rather difficult to be explained, I hope I may be allowed to express it in any way I can, and without sacrificing to the graces. Suppose a number of animalculæ, as a heap of mites in a rotten cheese, lying as close together as they possibly can (though the example should be of something more ‘drossy and divisible’ of something less reasonable, approaching nearer to pure sensation than we can conceive of any creature that exercises the functions of the meanest instinct). No one will contend that in this heap of living matter there is any idea or intimation of the number, position, or intricate involutions of that little, lively, restless tribe. This idea is evidently not contained in any of the parts separately, nor is it contained in all of them put together. That is, the aggregate of many actual sensations is, we here plainly see, a totally different thing from the collective idea, comprehension or consciousness of those sensations, as connected together into one whole, or of any of their relations to each other. We may go on multiplying sensations to the end of time, without ever advancing one step in the other process, or producing a single thought. But in what, I would ask, does this supposition differ from that of many distinct particles of matter, full of animation, tumbling about, and pressing against each other, in the same brain, except that we make use of this brain as a common medium to unite their different desultory actions in the same general principle of thought or consciousness—that is, understanding? Or, if this comparison should be thought not courtly enough, let us imagine one of Mrs. Salmon’s full faced, comely wax figures, sitting in its chair of state, to be suddenly endued with life and physical organization but nothing more. Such an unaccountable lusus naturæ would answer exactly to the theory of modern metaphysicians, or would be capable of receiving feelings or impressions by its different organs, but would be totally void of any reflection upon them. It would be only a bloated mass of listless sensation, a sordid compound of proud flesh and irritable humours, a mere animal existence, a living automation, crawling all over with morbid feelings, but without the least ray of understanding, or any knowledge of itself or of the things around, incapable of consistency of character or purpose, of foresight, deliberation, sympathy, and of all that distinguishes human reason or dignifies human nature!
Besides actual, sensible impressions, I suppose that there is a common principle of thought, a superintending faculty, which alone perceives the relations of things and enables us to comprehend their connections, forms, and masses. This faculty is properly the understanding, and it is by means of this faculty that man indeed becomes a reasonable soul. Without this surrounding and forming power, we could never conceive the idea of any one object, as of a table or a chair, a blade of grass or a grain of sand. Every one of these includes a certain configuration, hardness, colour, size, &c. i.e. impressions of different things, received by different senses, which must be put together by the understanding before they can be referred to any particular object, or considered as one idea. Without this faculty, all our ideas would be necessarily decomposed, and crumbled down into their original elements and fluxional parts. We could assuredly in this case never connect the different links in a chain of reasoning together, for the very links of which this chain must consist would be ground to powder. We could neither form any comparison between our ideas, nor have any ideas to compare. There would be an infinite divisibility in the impressions of the mind, as well as in the parts of material objects. Each separate impression must remain absolutely simple and distinct, unknown to and unconscious of the rest, shut up in the narrow cell of its own individuality. No two of these atomic impressions could ever club together to form even a sensible point, much less should we be able to arrive at any of the larger masses or nominal descriptions of things. The most that sensation could possibly do for us would be to furnish the mind with ideas of some of those which Mr. Locke calls the simple qualities of objects, as of colour or pressure, though not as a general notion or diffused feeling, for it is certain that no one impression could ever contain more than the tinge of a single ray of light, or the puncture of a single particle of matter. Perhaps we might in this way be supposed to possess an infinite number of microscopic impressions and fractions of ideas, but there being nothing to arrange or bind them together, the whole would present only a disjointed mass of blind, unconscious confusion. All nature, all objects, all parts of all objects, would be equally ‘without form and void.’ The mind alone is formative, to use the expression of Kant; or it is that which by its pervading and elastic energy unfolds and expands our ideas, that gives order and consistency to them, that assigns to every part its proper place, and fixes it there, and that frames the idea of the whole. Or in other words, it is the understanding alone that perceives relation, but every object is made up of a bundle of relations. In short, there is no object or idea which does not consist of a number of parts arranged in a certain manner, but of this arrangement the parts themselves cannot be sensible. To make each part conscious of its relation to all the rest is to suppose an infinite number of intellects instead of one; and to say that a knowledge or perception of each part separately without a reference to the rest can produce a conception of the whole, is a contradiction in terms.
Ideas then are the offspring of the understanding, not of the senses. An idea necessarily implies, not only a number of distinct positive impressions, but some bond of union between them, some internal conscious principle to which they are alike communicated, and which grasps, overlooks, and comprehends the whole. The idea of a square, for example, is not the same thing with the compound impression made by the figure on the senses. For the immediate impression of any one of the sides cannot, as a mere sensation, be accompanied with an additional knowledge or reflex image of the remaining three sides, but is a perfectly distinct, physical thing; neither can the actual coexistence of all these impressions be accompanied with a consciousness of their mutual relations to each other, i.e. with an idea of the whole, without supposing some general representative faculty, to which these distinct impressions are referred.
Otherwise, different impressions made on the same organized or sentient being would no more produce the slightest continuity of thought or idea of the same object than different physical impressions conveyed to different organized beings would produce an immediate consciousness of these different objects or of the relations between them. If to have sensations were the same thing as to compare them, then different persons seeing different objects might without any communication make an exact comparison between them. If to have the sensible impression of the different parts of an object were the same thing as to form an idea of it, then different persons looking at the two halves of any object would be able to compound an idea of the whole between them, though each of them was perfectly unconscious of what was passing in the other’s mind. Unless we suppose some faculty of this sort which opens a direct communication between our perceptions, so that the same thinking principle is at the same time cognisant of different impressions, and of their relations to each other, 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 very idea of individuality could never have been so much as conceived of, if there were no other connection between our perceptions, than that which arises from the juxtaposition of the particles of matter on which they are actually impressed, or from ‘a physical consideration of the senses and the mind.’ The mind in this case consisting of nothing more than a succession of material points, each part would be sensible of the corresponding part of any object which might be impressed upon it, but could certainly know nothing of the impression which was made on any other part of the same organic substance, except by its communication to the same general principle of understanding. Ideas would exist in the mind, like tapestry figures or pictures in a gallery, without a spectator. On this hypothesis, I perfectly agree with Mr. Horne Tooke, that it would be as absurd to talk of a complex idea as of a complex star; for each impression or sensation must be as perfectly distinct from, and unconnected with the rest, as the stars that compose a constellation. One idea or impression would have no more connection with any other, than if it were parcel of another intellect, or floated in the region of the moon.[[11]]
It is strange that Mr. Locke should rank among simple ideas that of number, which he defines to be the idea of unity repeated. But how the impression of successive or distinct units should ever give the idea of repetition, unless the former instances are borne in mind, I have not the slightest conception. There might be an endless transition from one unit to another, but no addition made or ideal aggregate formed. As well might we suppose, that a body of an inch diameter, by shifting from place to place, may enlarge its dimensions to a foot or a mile, as that a succession of units, perceived separately, should produce the complex idea of multitude. On the mechanical hypothesis, the mind can receive or attend to but one impression at a time, and the idea of number would be too mighty for it. Though Mr. Locke constantly supposes the mind to perceive relations, and explains its common operations on this principle, there is but one place in his work in which he seems to have been upon the point of discovering that this principle lies at the foundation of, and is absolutely necessary to all our ideas whatever. He says, in the beginning of his chapter on Power, which he classes among simple ideas, ‘I confess power includes in it some kind of relation (a relation to action or change), as, indeed, which of our ideas, of what kind soever, when attentively considered, does not? For our ideas of extension, duration, and number, do they not all contain in them a secret relation of the parts? Figure and motion have something relative in them much more visibly; and sensible qualities, as colours and smells, what are they but the powers of different bodies in relation to our perception? And if considered in the things themselves, do they not depend on the bulk, figure, texture, and motion of the parts? All which include some kind of relation in them. Our idea, therefore, of power, I think, may well have a place amongst other simple ideas, and be considered as one of them, being one of those that make a principal ingredient in our complex ideas of substances.’—Essay on Human Understanding, vol. i. p. 234.
That is to say, in other words, the idea of power, though confessedly complex, according to Mr. Locke, as depending on the changes we observe produced by one thing on another, is to pass for a simple idea, because it has as good a right to this denomination as other complex ideas, which are usually classed as simple ones. It is thus that the inquiring mind seems to be always hovering on the brink of truth: but timidity, or indolence, or prejudice, makes us shrink back, unwilling to trust ourselves to the fathomless abyss.