Kant, however, having caught the original scent from Hume, was more fortunate. He saw, at a glance, that here was a test applied to the Lockian philosophy, which showed, at the very least, its insufficiency. If it were good even for so much as it explained—which Burke is disposed to receive as a sufficient warrant for the favourable reception of a new hypothesis—at any rate, it now appeared that there was something which it could not explain. But next, Kant took a large step in advance proprio morte. Reflecting upon the one idea adduced by Hume, as transcending the ordinary source of ideas, he began to ask himself, whether it were likely that this idea should stand alone? Were there not other ideas in the same predicament; other ideas including the same element of necessity, and, therefore, equally disowning the parentage assigned by Locke? Upon investigation, he found that there were: he found that there were eleven others in exactly the same circumstances. The entire twelve he denominated categories; and the mode by which he ascertained their number—that there were so many and no more—is of itself so remarkable as to merit notice in the most superficial sketch. But, in fact, this one explanation will put the reader in possession of Kant's system, so far as he could understand it without an express and toilsome study. With this explanation, therefore, of the famous categories, I shall close my slight sketch of the system. Has the reader ever considered the meaning of the term Category—a term so ancient and so venerable from its connection with the most domineering philosophy that has yet appeared amongst men? The doctrine of the Categories (or, in its Roman appellation, of the Predicaments), is one of the few wrecks from the Peripatetic philosophy which still survives as a doctrine taught by public authority in the most ancient academic institutions of Europe. It continues to form a section in the code of public instruction; and perhaps under favour of a pure accident. For though, strictly speaking, a metaphysical speculation, it has always been prefixed as a sort of preface to the Organon (or logical treatises) of Aristotle, and has thus accidentally shared in the immortality conceded to that most perfect of human works. Far enough were the Categories from meriting such distinction. Kant was well aware of this: he was aware that the Aristotelian Categories were a useless piece of scholastic lumber: unsound in their first conception; and, though illustrated through long centuries by the schoolmen, and by still earlier Grecian philosophers, never in any one known instance turned to a profitable account. Why, then, being aware that even in idea they were false, besides being practically unsuitable, did Kant adopt or borrow a name laden with this superfetation of reproach—all that is false in theory superadded to all that is useless in practice? He did so for a remarkable reason: he felt, according to his own explanation, that Aristotle had been groping [the German word expressive of his blind procedure is herumtappen]—groping in the dark, but under a semi-conscious instinct of truth. Here is a most remarkable case or situation of the human intellect, happening alike to individuals and to entire generations—in the situation of yearning or craving, as it were, for a great idea as yet unknown, but dimly and uneasily prefigured. Sometimes the very brink, as it may be called, of such an idea is approached; sometimes it is even imperfectly discovered; but with marks in the very midst of its imperfections, which serve as indications to a person coming better armed for ascertaining the sub-conscious thought which had governed their tentative motions. As it stands in Aristotle's scheme, the idea of a category is a mere lifeless abstraction. Rising through a succession of species to genera, and from these to still higher genera, you arrive finally at a highest genus—a naked abstraction, beyond which no further regress is possible. This highest genus, this genus generalissimum, is, in peripatetic language, a category; and no purpose or use has ever been assigned to any one of these categories, of which ten were enumerated at first, beyond that of classification—i. e. a purpose of mere convenience. Even for as trivial a purpose as this, it gave room for suspecting a failure, when it was afterwards found that the original ten categories did not exhaust the possibilities of the case; that other supplementary categories (post-prædicamenti) became necessary. And, perhaps, 'more last words' might even yet be added, supplementary supplements, and so forth, by a hair-splitting intellect. Failures as gross as these, revisals still open to revision, and amendments calling for amendments, were at once a broad confession that here there was no falling in with any great law of nature. The paths of nature may sometimes be arrived at in a tentative way; but they are broad and determinate; and, when found, vindicate themselves. Still, in all this erroneous subtilisation, and these abortive efforts, Kant perceived a grasping at some real idea—fugitive indeed and coy, which had for the present absolutely escaped; but he caught glimpses of it continually in the rear; he felt its necessity to any account of the human understanding that could be satisfactory to one who had meditated on Locke's theory as probed and searched by Leibnitz. And in this uneasy state—half sceptical, half creative, rejecting and substituting, pulling down and building up—what was in sum and finally the course which he took for bringing his trials and essays to a crisis? He states this himself, somewhere in the Introduction to his Critik der reinen Vernunft; and the passage is a memorable one. Fifteen years at the least have passed since I read it; and, therefore, I cannot pretend to produce the words; but the substance I shall give; and I appeal to the candour of all his readers, whether they have been able to apprehend his meaning. I certainly did not for years. But, now that I do, the passage places his procedure in a most striking and edifying light. Astronomers, says Kant, had gone on for ages, assuming that the earth was the central body of our system; and insuperable were the difficulties which attended that assumption. At length, it occurred to try what would result from inverting the assumption. Let the earth, instead of offering a fixed centre for the revolving motions of other heavenly bodies, be supposed itself to revolve about some one of these, as the sun. That supposition was tried, and gradually all the phenomena which, before, had been incoherent, anomalous, or contradictory, began to express themselves as parts of a most harmonious system. 'Something,' he goes on to say, 'analogous to this I have practised with regard to the subject of my inquiry—the human understanding. All others had sought their central principle of the intellectual phenomena out of the understanding, in something external to the mind. I first turned my inquiries upon the mind itself. I first applied my examination to the very analysis of the understanding.' In words, not precisely these, but pretty nearly equivalent to them, does Kant state, by contradistinction, the value and the nature of his own procedure. He first, according to his own representation, thought of applying his investigation to the mind itself. Here was a passage which for years (I may say) continued to stagger and confound me. What! he, Kant, in the latter end of the 18th century, about the year 1787—he the first who had investigated the mind! This was not arrogance so much as it was insanity. Had he said—I, first, upon just principles, or with a fortunate result, investigated the human understanding, he would have said no more than every fresh theorist is bound to suppose, as his preliminary apology for claiming the attention of a busy world. Indeed, if a writer, on any part of knowledge, does not hold himself superior to all his predecessors, we are entitled to say—Then, why do you presume to trouble us? It may look like modesty, but is, in effect, downright effrontery for you to think yourself no better than other critics; you were at liberty to think so whilst no claimant of public notice—as being so, it is most arrogant in you to be modest. This would be the criticism applied justly to a man who, in Kant's situation, as the author of a new system, should use a language of unseasonable modesty or deprecation. To have spoken boldly of himself was a duty; we could not tolerate his doing otherwise. But to speak of himself in the exclusive terms I have described, does certainly seem, and for years did seem to myself, little short of insanity. Of this I am sure that no student of Kant, having the passage before him, can have known heretofore what consistent, what rational interpretation to give it; and, in candour, he ought to own himself my debtor for the light he will now receive. Yet, so easy is it to imagine, after a meaning is once pointed out, and the station given from which it shows itself as the meaning—so easy, under these circumstances, is it to imagine that one has, or that one could have, found it for one's self—that I have little expectation of reaping much gratitude for my explanation. I say this, not as of much importance one way or the other in a single case of the kind, but because a general consideration of this nature has sometimes operated to make me more indifferent or careless as to the publication of commentaries on difficult systems, when I had found myself able to throw much light on the difficulties. The very success with which I should have accomplished the task—the perfect removal of the obstacles in the student's path—were the very grounds of my assurance-that the service would be little valued. For I have found what it was occasionally, in conversation, to be too luminous—to have explained, for instance, too clearly a dark place in Ricardo. In such a case, I have known a man of the very greatest powers, mistake the intellectual effort he had put forth to apprehend my elucidation, and to meet it half way, for his own unassisted conquest over the difficulties; and, within an hour or two after, I have had, perhaps, to stand, as an attack upon myself, arguments entirely and recently furnished by myself. No case is more possible: even to apprehend a complex explanation, a man cannot be passive; he must exert considerable energy of mind; and, in the fresh consciousness of this energy, it is the most natural mistake in the world for him to feel the argument which he has, by considerable effort, appropriated to be an argument which he has originated. Kant is the most unhappy champion of his own doctrines, the most infelicitous expounder of his own meaning, that has ever existed. Neither has any other commentator succeeded in throwing a moonlight radiance upon his philosophy. Yet certain I am, that, were I, or any man, to disperse all his darkness, exactly in that proportion in which we did so—exactly in the proportion in which we smoothed all hindrances—exactly in that proportion would it cease to be known or felt that there had ever been any hindrances to be smoothed. This, however, is digression, to which I have been tempted by the interesting nature of the grievance. In a jesting way, this grievance is obliquely noticed in the celebrated couplet—
'Had you seen but these roads before they were made,
You'd lift up your hands and bless Marshal Wade.'
The pleasant bull here committed conceals a most melancholy truth, and one of large extent. Innumerable are the services to truth, to justice, or society, which never can be adequately valued by those who reap their benefits, simply because the transition from the early and bad state to the final or improved state cannot be retraced or kept alive before the eyes. The record perishes. The last point gained is seen; but the starting-point, the points from which it was gained, is forgotten. And the traveller never can know the true amount of his obligations to Marshal Wade, because, though seeing the roads which the Marshal has created, he can only guess at those which he superseded. Now, returning to this impenetrable passage of Kant, I will briefly inform the reader that he may read it into sense by connecting it with a part of Kant's system, from which it is in his own delivery entirely dislocated. Going forwards some thirty or forty pages, he will find Kant's development of his own categories. And, by placing in juxtaposition with that development this blind sentence, he will find a reciprocal light arising. All philosophers, worthy of that name, have found it necessary to allow of some great cardinal ideas that transcended all the Lockian origination—ideas that were larger in their compass than any possible notices of sense or any reflex notices of the understanding; and those who have denied such ideas, will be found invariably to have supported their denial by a vitium subreptionis, and to have deduced their pretended genealogies of such ideas by means of a petitio principii—silently and stealthily putting into some step of their leger-de-main process everything that they would pretend to have extracted from it. But, previously to Kant, it is certain that all philosophers had left the origin of these higher or transcendent ideas unexplained. Whence came they? In the systems to which, Locke replies, they had been called innate or connate. These were the Cartesian systems. Cudworth, again, who maintained certain 'immutable ideas' of morality, had said nothing about their origin; and Plato had supposed them to be reminiscences from some higher mode of existence. Kant first attempted to assign them an origin within the mind itself, though not in any Lockian fashion of reflection upon sensible impressions. And this is doubtless what he means by saying that he first had investigated the mind—that is, he first for such a purpose.
Where, then, is it, in what act or function of the mind, that Kant finds the matrix of these transcendent ideas? Simply in the logical forms of the understanding. Every power exerts its agency under some laws—that is, in the language of Kant, by certain forms. We leap by certain laws—viz. of equilibrium, of muscular motion, of gravitation. We dance by certain laws. So also we reason by certain laws. These laws, or formal principles, under a particular condition, become the categories.
Here, then, is a short derivation, in a very few words, of those ideas transcending sense, which all philosophy, the earliest, has been unable to dispense with, and yet none could account for. Thus, for example, every act of reasoning must, in the first place, express itself in distinct propositions; that is, in such as contain a subject (or that concerning which you affirm or deny something), a predicate (that which you affirm or deny), and a copula, which connects them. These propositions must have what is technically called, in logic, a certain quantity, or compass (viz. must be universal, particular, or singular); and again they must have what is called quality (that is, must be affirmative, or negative, or infinite): and thus arises a ground for certain corresponding ideas, which are Kant's categories of quantity and quality.
But, to take an illustration more appropriately from the very idea which first aroused Kant to the sense of a vast hiatus in the received philosophies—the idea of cause, which had been thrown as an apple of discord amongst the schools, by Hume. How did Kant deduce this? Simply thus: it is a doctrine of universal logic, that there are three varieties of syllogism—viz. 1st, Categoric, or directly declarative [A is B]; 2nd, Hypothetic, or conditionally declarative [If C is D, then A is B]; 3rd, Disjunctive, or declarative, by means of a choice which exhausts the possible cases [A is either B, or C, or D; but not C or D; ergo B]. Now, the idea of causation, or, in Kant's language, the category of Cause and Effect, is deduced immediately, and most naturally, as the reader will acknowledge on examination, from the 2nd or hypothetic form of syllogism, when the relation of dependency is the same as in the idea of causation, and the necessary connection a direct type of that which takes place between a cause and its effect.
Thus, then, without going one step further, the reader will find grounds enough for reflection and for reverence towards Kant in these two great results: 1st, That an order of ideas has been established, which all deep philosophy has demanded, even when it could not make good its claim. This postulate is fulfilled. 2ndly, The postulate is fulfilled without mysticism or Platonic reveries. Ideas, however indispensable to human needs, and even to the connection of our thoughts, which came to us from nobody knew whence, must for ever have been suspicious; and, as in the memorable instance cited from Hume, must have been liable for ever to a question of validity. But, deduced as they now are from a matrix within our own minds, they cannot reasonably fear any assaults of scepticism.
Here I shall stop. A reader new to these inquiries may think all this a trifle. But he who reflects a little, will see that, even thus far, and going no step beyond this point, the Kantian doctrine of the Categories answers a standing question hanging aloof as a challenge to human philosophy, fills up a lacuna pointed out from the era of Plato. It solves a problem which has startled and perplexed every age: viz. this—that man is in possession, nay, in the hourly exercise, of ideas larger than he can show any title to. And in another way, the reader may measure the extent of this doctrine, by reflecting that, even so far as now stated, it is precisely coextensive with the famous scheme of Locke. For what is the capital thesis of that scheme? Simply this—that all necessity for supposing immediate impressions made upon our understandings by God, or other supernatural, or antenatal, or connatal, agencies, is idle and romantic; for that, upon examining the furniture of our minds, nothing will be found there which cannot adequately be explained out of our daily experience; and, until we find something that cannot be solved by this explanation, it is childish to go in quest of higher causes. Thus says Locke: and his whole work, upon its first plan, is no more than a continual pleading of this single thesis, pursuing it through all the plausible objections. Being, therefore, as large in its extent as Locke, the reader must not complain of the transcendental scheme as too narrow, even in that limited section of it here brought under his notice.
For the purpose of repelling it, he must do one of two things: either he must show that these categories or transcendent notions are not susceptible of the derivation and genesis here assigned to them—that is, from the forms of the logos or formal understanding; or, if content to abide by that derivation, he must allege that there are other categories besides those enumerated, and unprovided with any similar parentage.
Thus much in reply to him who complains of the doctrine here stated; as, 1st, Too narrow; or, 2nd, As insufficiently established. But, 3rd, in reply to him who wishes to see it further pursued or applied, I say that the possible applications are perhaps infinite. With respect to those made by Kant himself, they are chiefly contained in his main and elementary work, the Critik der reinen Vernunft; and they are of a nature to make any man melancholy. Indeed, let a man consider merely this one notion of causation; let him reflect on its origin; let him remember that, agreeably to this origin, it follows that we have no right to view anything in rerum naturâ as objectively, or in itself a cause; that when, upon the fullest philosophic proof, we call A the cause of B, we do in fact only subsume A under the notion of a cause; we invest it with that function under that relation, that the whole proceeding is merely with respect to a human understanding, and by way of indispensable nexus to the several parts of our experience; finally, that there is the greatest reason to doubt, whether the idea of causation is at all applicable to any other world than this, or any other than a human experience. Let a man meditate but a little on this or other aspects of this transcendental philosophy, and he will find the steadfast earth itself rocking as it were beneath his feet; a world about him, which is in some sense a world of deception; and a world before him, which seems to promise a world of confusion, or 'a world not realised.' All this he might deduce for himself without further aid from Kant. However, the particular purposes to which Kant applies his philosophy, from the difficulties which beset them, are unfitted for anything below a regular treatise. Suffice it to say here, that, difficult as these speculations are from one or two embarrassing doctrines on the Transcendental Consciousness, and depressing as they are from their general tendency, they are yet painfully irritating to the curiosity, and especially so from a sort of experimentum crucis, which they yield in the progress of their development on behalf of the entire doctrine of Kant—a test which, up to this hour, has offered defiance to any hostile hand. The test or defiance which I speak of, takes the shape of certain antinomies (so they are termed), severe adamantine arguments, affirmative and negative, on two or three celebrated problems, with no appeal to any possible decision, but one, which involves the Kantian doctrines. A quæstio vexata is proposed—for instance, the infinite divisibility of matter; each side of this question, thesis and antithesis, is argued; the logic is irresistible, the links are perfect, and for each side alternately there is a verdict, thus terminating in the most triumphant reductio ad absurdum—viz. that A, at one and the same time and in the same sense, is and is not B, from which no escape is available, but through a Kantian solution. On any other philosophy, it is demonstrated that this opprobrium of the human understanding, this scandal of logic, cannot be removed. This celebrated chapter of antinomies has been of great service to the mere polemics of the transcendental philosophy: it is a glove or gage of defiance, constantly lying on the ground, challenging the rights of victory and supremacy so long as it is not taken up by any antagonist, and bringing matters to a short decision when it is.
One section, and that the introductory section, of the transcendental philosophy, I have purposely omitted, though in strictness not to be insulated or dislocated from the faithful exposition even of that which I have given. It is the doctrine of Space and Time. These profound themes, so confounding to the human understanding, are treated by Kant under two aspects—1st, as Anchauungen, or Intuitions (so the German word is usually translated for want of a better); 2ndly, as forms, à priori, of all our other intuitions. Often have I laughed internally at the characteristic exposure of Kant's style of thinking—that he, a man of so much worldly sagacity, could think of offering, and of the German scholastic habits, that any modern nation could think of accepting such cabalistical phrases, such a true and very 'Ignotium per Ignotius,' in part payment of an explanatory account of Time and Space. Kant repeats these words—as a charm before which all darkness flies; and he supposes continually the case of a man denying his explanations or demanding proofs of them, never once the sole imaginable case—viz. of all men demanding an explanation of these explanations. Deny them! Combat them! How should a man deny, why should he combat, what might, for anything to the contrary appearing, contain a promissory note at two months after date for 100 guineas? No; it will cost a little preliminary work before such explanations will much avail any scheme of philosophy, either for the pro or the con. And yet I do myself really profess to understand the dark words; and a great service it would be to sound philosophy amongst us, if this one word anschauung were adequately unfolded and naturalised (as naturalised it might be) in the English philosophic dictionary, by some full Grecian equivalent. Strange that no man acquainted with German philosophy, should yet have been struck by the fact—or, being struck, should not have felt it important to call public attention to the fact of our inevitable feebleness in a branch of study for which as yet we want the indispensable words. Our feebleness is at once argued by this want, and partly caused. Meantime, as respects the Kantian way of viewing space, by much the most important innovation which it makes upon the old doctrines is—that it considers space as a subjective not an objective aliquid; that is, as having its whole available foundation lying ultimately in ourselves, not in any external or alien tenure. This one distinction, as applied to space, for ever secures (what nothing else can secure or explain) the cogency of geometrical evidence. Whatever is true for any determinations of a space originally included in ourselves, must be true for such determinations for ever, since they cannot become objects of consciousness to us but in and by that very mode of conceiving space, that very form of schematism which originally presented us with these determinations of space, or any whatever. In the uniformity of our own space-conceiving faculty, we have a pledge of the absolute and necessary uniformity (or internal agreement among themselves) of all future or possible determinations of space; because they could not otherwise become to us conceivable forms of space, than by adapting themselves to the known conditions of our conceiving faculty. Here we have the necessity which is indispensable to all geometrical demonstration: it is a necessity founded in our human organ, which cannot admit or conceive a space, unless as preconforming to these original forms or schematisms. Whereas, on the contrary, if space were something objective, and consequently being a separate existence, independent of a human organ, then it is altogether impossible to find any intelligible source of obligation or cogency in the evidence—such as is indispensable to the very nature of geometrical demonstration. Thus we will suppose that a regular demonstration has gradually, from step to step downwards, through a series of propositions—No. 8 resting upon 7, that upon 5, 5 upon 3—at length reduced you to the elementary axiom, that Two straight lines cannot enclose a space. Now, if space be subjective originally—that is to say, founded (as respects us and our geometry) in ourselves—then it is impossible that two such lines can enclose a space, because the possibility of anything whatever relating to the determinations of space is exactly co-extensive with (and exactly expressed by) our power to conceive it. Being thus able to affirm its impossibility universally, we can build a demonstration upon it. But, on the other hypothesis, of space being objective, it is impossible to guess whence we are to draw our proof of the alleged inaptitude in two straight lines for enclosing a space. The most we could say is, that hitherto no instance has been found of an enclosed space circumscribed by two straight lines. It would not do to allege our human inability to conceive, or in imagination to draw, such a circumscription. For, besides that such a mode of argument is exactly the one supposed to have been rejected, it is liable to this unanswerable objection, so long as space is assumed to have an objective existence, viz. that the human inability to conceive such a possibility, only argues (what in fact is often found in other cases) that the objective existence of space—i. e. the existence of space in itself, and in its absolute nature—is far larger than its subjective existence—i. e. than its mode of existing quoad some particular subject. A being more limited than man might be so framed as to be unable to conceive curve lines; but this subjective inaptitude for those determinations of space would not affect the objective reality of curves, or even their subjective reality for a higher intelligence. Thus, on the hypothesis of an objective existence for space, we should be thrown upon an ocean of possibilities, without a test for saying what was—what was not possible. But, on the other hypothesis, having always in the last resort what is subjectively possible or impossible (i. e. what is conceivable or not by us, what can or cannot be drawn or circumscribed by a human imagination), we have the means of demonstration in our power, by having the ultimate appeals in our power to a known uniform test—viz. a known human faculty.
This is no trifling matter, and therefore no trifling advantage on the side of Kant and his philosophy, to all who are acquainted with the disagreeable controversies of late years among French geometricians of the first rank, and sometimes among British ones, on the question of mathematical evidence. Legendre and Professor Leslie took part in one such a dispute; and the temper in which it was managed was worthy of admiration, as contrasted with the angry controversies of elder days, if, indeed, it did not err in an opposite spirit, by too elaborate and too calculating a tone of reciprocal flattery. But think as we may of the discussion in this respect, most assuredly it was painful to witness so infirm a philosophy applied to an interest so mighty. The whole aerial superstructure—the heaven-aspiring pyramid of geometrical synthesis—all tottered under the palsying logic of evidence, to which these celebrated mathematicians appealed. And wherefore?—From the want of any philosophic account of space, to which they might have made a common appeal, and which might have so far discharged its debt to truth, as at least to reconcile its theory with the great outstanding phenomena in the most absolute of sciences. Geometry is the science of space: therefore, in any philosophy of space, geometry is entitled to be peculiarly considered, and used as a court of appeal. Geometry has these two further claims to distinction—that, 1st, It is the most perfect of the sciences, so far as it has gone; and, 2ndly, That it has gone the farthest. A philosophy of space, which does not consider and does not reconcile to its own doctrines the facts of geometry, which, in the two points of beauty and of vast extent, is more like a work of nature than of man, is, primâ facie, of no value. A philosophy of space might be false, which should harmonise with the facts of geometry—it must be false, if it contradict them. Of Kant's philosophy it is a capital praise, that its very opening section—that section which treats the question of space, not only quadrates with the facts of geometry, but also, by the subjective character which it attributes to space, is the very first philosophic scheme which explains and accounts for the cogency of geometrical evidence.