1. The man of common sense, (so called,) who aspires to be somewhat of a philosopher, will face the question boldly, and will say, "I feel that colour and hardness, for instance, lie entirely within the sphere of sense, and are mere modifications of my subjective nature. At the same time, feel that colour and hardness constitute a real object, which exists out of the sphere of sense, independently of me and all my modifications. How this should be, I know not; I merely state the fact as I imagine myself to find it. The modus is beyond my comprehension." This man belongs to the school of Natural Realists. If he merely affirmed or postulated a miracle in what he uttered, we should have little to say against him, (for the whole process of sensation is indeed miraculous.) But he postulates more than a miracle; he postulates a contradiction, in the very contemplation of which our reason is unhinged.
2. Another man will deny that our sensations ever transcend the sphere of sense, or attain a real objective existence. "Colour, hardness, figure, and so forth," he will say, "are generated within the sphere of sense, in obedience to its own original laws. They form integral parts of the sphere; and he who endeavours to construe them to his own mind as embodied in extrinsic independent existences, must for ever be foiled in the attempt." This man declines giving any answer to the problem. We ask, how can our sensations be embodied in distinct permanent realities? And he replies, that they never are and never can be so embodied. This man is an Idealist—or as we would term him, (to distinguish him from another species about to be mentioned, of the same genus,) an Acosmical idealist; that is, an Idealist who absolutely denies the existence of an independent material world.
3. A third man will postulate as the cause of our sensations of hardness, colour, &c., a transcendent something, of which he knows nothing, except that he feigns and fables it as lying external to the sphere of sense: and then, by referring our sensations to this unknown cause, he will obtain for them, not certainly the externality desiderated, but a quasi-externality, which he palms off upon himself and us as the best that can be supplied. This man is Cosmothetical Idealist: that is, an Idealist who postulates an external universe as the unknown cause of certain modifications we are conscious of within ourselves, and which, according to his view, we never really get beyond. This species of speculator is the commonest, but he is the least trustworthy of any; and his fallacies are all the more dangerous by reason of the air of plausibility with which they are invested. From first to last, he represents us as the dupes of our own perfidious nature. By some inexplicable process of association, he refers certain known effects to certain unknown causes; and would thus explain to us how these effects (our sensations) come to assume, as it were, the character of external objects. But we know not "as it were." Away with such shuffling phraseology. There is nothing either of reference, or of inference, or of quasi-truthfulness in our apprehension of the material universe. It is ours with a certainty which laughs to scorn all the deductions of logic, and all the props of hypothesis. What we wish to know is, how our subjective affections can be, not as it were, but in God's truth, and in the strict, literal, earnest, and unambiguous sense of the words, real independent, objective existences. This is what the cosmothetical idealist never can explain, and never attempts to explain.
4. We now come to the answer which the reader, who has followed us thus far, will be prepared to find us putting forward as by far the most important of any, and as containing in fact the very kernel of the solution. A fourth man will say—"If the whole sphere of sense could only be withdrawn inwards—could be made to fall somewhere within itself—then the whole difficulty would disappear, and the problem would be solved at once. The sensations which existed previous to this retraction or withdrawal, would then, of necessity, fall without the sphere of sense, ( see our second diagram;) and in doing so, they would necessarily assume a totally different aspect from that of sensations. They would be real independent objects: and (what is the important part of the demonstration) they would acquire this status without overstepping by a hair's-breadth the primary limits of the sphere. Were such phraseology allowable, we should say that the sphere has understepped itself, and in doing so, has left its former contents high and dry, and stamped with all the marks which can characterize objective existences."
Now the reader will please to remark, that we are very far from desiring him to accept this last solution at our bidding. Our method, we trust, is any thing but dogmatical. We merely say, that if this can be shown to be the case, then the demonstration which we are in the course of unfolding, will hardly fail to recommend itself to his acceptance. Whether or not it is the case, can only be established by an appeal to our experience.
We ask, then—does experience inform us, or does she not, that the sphere of sense falls within, and very considerably within, itself? But here it will be asked—what meaning do we attach to the expression, that sense falls within its own sphere? These words, then, we must first of all explain. Every thing which is apprehended as a sensation—such as colour, figure, hardness, and so forth—falls within the sentient sphere. To be a sensation, and to fall within the sphere of sense, are identical and convertible terms. When, therefore, it is asked—does the sphere of sense ever fall within itself? this is equivalent to asking—do the senses themselves ever become sensations? Is that which apprehends sensations ever itself apprehended as a sensation? Can the senses he seized on within the limits of the very circle which they prescribe? If they cannot, then it must be admitted that the sphere of sense never falls within itself, and consequently that an objective reality—i.e. a reality extrinsic to that sphere—can never be predicated or secured for any part of its contents. But we conceive that only one rational answer can be returned to this question. Does not experience teach us, that much if not the whole of our sentient nature becomes itself in turn a series of sensations? Does not the sight—that power which contains the whole visible space, and embraces distances which no astronomer can compute—does it not abjure its high prerogative, and take rank within the sphere of sense—itself a sensation—when revealed to us in the solid atom we call the eye? Here it is the touch which brings the sight within, and very far within, the sphere of vision. But somewhat less directly, and by the aid of the imagination, the sight operates the same introtraction (pardon the coinage) upon itself. It ebbs inwards, so to speak, from all the contents that were given in what may be called its primary sphere. It represents itself, in its organ, as a minute visual sensation, out of, and beyond which, are left lying the great range of all its other sensations. By imagining the sight as a sensation of colour, we diminish it to a speck within the sphere of its own sensations; and as we now regard the sense as for ever enclosed within this small embrasure, all the other sensations which were its, previous to our discovery of the organ, and which are its still, are built up into a world of objective existence, necessarily external to the sight, and altogether out of its control. All sensations of colour are necessarily out of one another. Surely, then, when the sight is subsumed under the category of colour—as it unquestionably is whenever we think of the eye—surely all other colours must, of necessity, assume a position external to it; and what more is wanting to constitute that real objective universe of light and glory in which our hearts rejoice?
We can, perhaps, make this matter still plainer by reverting to our old illustration. Our first exposition of the question was designed to exhibit a general view of the case, through the medium of a dead symbolical figure. This proved nothing, though we imagine that it illustrated much. Our second exposition exhibited the illustration in its application to the living sphere of sensation in general; and this proved little. But we conceive that therein was foreshadowed a certain procedure, which, if it can be shown from experience to be the actual procedure of sensation in detail, will prove all that we are desirous of establishing. We now, then, descend to a more systematic exposition of the process which (so far as our experience goes, and we beg to refer the reader to his own) seems to be involved in the operation of seeing. We dwell chiefly upon the sense of sight, because it is mainly through its ministrations that a real objective universe is given to us. Let the circle A be the whole circuit of vision. We may begin by calling it the eye, the retina, or what we will. Let it be provided with the ordinary complement of sensations—the colours X Y Z. Now, we admit that these sensations cannot be extruded beyond the periphery of vision; and yet we maintain that, unless they be made to fall on the outside of that periphery, they cannot become real objects. How is this difficulty—this contradiction—to be overcome? Nature overcomes it, by a contrivance as simple as it is beautiful. In the operation of seeing, admitting the canvass or background of our picture to be a retina, or what we will, with a multiplicity of colours depicted upon it, we maintain that we cannot stop here, and that we never do stop here. We invariably go on (such is the inevitable law of our nature) to complete the picture—that is to say, we fill in our own eye as a colour within the very picture which our eye contains—we fill it in as a sensation within the other sensations which occupy the rest of the field; and in doing so, we of necessity, by the same law, turn these sensations out of the eye; and they thus, by the same necessity, assume the rank of independent objective existences. We describe the circumference infinitely within the circumference; and hence all that lies on the outside of the intaken circle comes before us stamped with the impress of real objective truth. We fill in the eye greatly within the sphere of light, (or within the eye itself; if we insist on calling the primary sphere by this name,) and the eye thus filled in is the only eye we know any thing at all about, either from the experience of sight or of touch. How this operation is accomplished, is a subject of but secondary moment; whether it be brought about by the touch, by the eye itself, or by the imagination, is a question which might admit of much discussion; but it is one of very subordinate interest. The fact is the main thing—the fact that the operation is accomplished in one way or another—the fact that the sense comes before itself (if not directly, yet virtually) as one of its own sensations—that is the principal point to be attended to; and we apprehend that this fact is now placed beyond the reach of controversy.
To put the case in another light. The following considerations may serve to remove certain untoward difficulties in metaphysics and optics, which beset the path, not only of the uninitiated, but even of the professors of these sciences.
We are assured by optical metaphysicians, or metaphysical opticians, that, in the operations of vision, we never get beyond the eye itself, or the representations that are depicted therein. We see nothing, they tell us, but what is delineated within the eye. Now, the way in which a plain man should meet this statement, is this—he should ask the metaphysician what eye he refers to. Do you allude, sir, to an eye which belongs to my visible body, and forms a small part of the same; or do you allude to an eye which does not belong to my visible body, and which constitutes no portion thereof? If the metaphysician should say, that he refers to an eye of the latter description, then the plain man's answer should be—that he has no experience of any such eye—that he cannot conceive it—that he knows nothing at all about it—and that the only eye which he ever thinks or speaks of, is the eye appertaining to, and situated within, the phenomenon which he calls his visible body. Is this, then, the eye which the metaphysician refers to, and which he tells us we never get beyond? If it be—why, then, the very admission that this eye is a part of the visible body, (and what else can we conceive the eye to be?) proves that we must get beyond it. Even supposing that the whole operation were transacted within the eye, and that the visible body were nowhere but within the eye, still the eye which we invariably and inevitably fill in as belonging to the visible body, (and no other eye is ever thought of or spoken of by us,)—this eye, we say, must necessarily exclude the visible body, and all other visible things, from its sphere. Or, can the eye (always conceived of as a visible thing among other visible things) again contain the very phenomenon (i.e. the visible body) within which it is itself contained? Surely no one will maintain a position of such unparalleled absurdity as that.
The science of optics, in so far as it maintains, according to certain physiological principles, that in the operation of seeing we never get beyond the representations within the eye, is founded on the assumption, that the visible body has no visible eye belonging to it. Whereas we maintain, that the only eye that we have—the only eye we can form any conception of, is the visible eye that belongs to the visible body, as a part does to a whole; whether this eye be originally revealed to us by the touch, by the sight, by the reason, or by the imagination. We maintain, that to affirm we never get beyond this eye in the exercise of vision, is equivalent to asserting, that a part is larger than the whole, of which it is only a part—is equivalent to asserting, that Y, which is contained between X and Z, is nevertheless of larger compass than X and Z, and comprehends them both. The fallacy we conceive to be this, that the visible body can be contained within the eye, without the eye of the visible body also being contained therein. But this is a procedure, which no law, either of thought or imagination, will tolerate. If we turn the visible body, and all visible things, into the eye, we must turn the eye of the visible body also into the eye; a process which, of course, again turns the visible body, and all visible things, out of the eye. And thus the procedure eternally defeats itself. Thus the very law which appears to annihilate, or render impossible, the objective existence of visible things, as creations independent of the eye—this very law, when carried into effect with a thorough-going consistency, vindicates and establishes that objective existence, with a logical force, an iron necessity, which no physiological paradox can countervail.