51. THE CRITICAL PHILOSOPHY.--The German philosopher, Immanuel Kant (1724-1804), was moved, by the skeptical conclusions to which Hume"s philosophy seemed to lead, to seek a way of escape, somewhat as Reid was. But he did not take refuge in "Common Sense"; he developed an ingenious doctrine which has had an enormous influence in the philosophical world, and has given rise to a Kantian literature of such proportions that no man can hope to read all of it, even if he devotes his life to it. In Germany and out of it, it has for a hundred years and more simply rained books, pamphlets, and articles on Kant and his philosophy, some of them good, many of them far from clear and far from original. Hundreds of German university students have taken Kant as the subject of the dissertation by which they hoped to win the degree of Doctor of Philosophy;--I was lately offered two hundred and seventy-four such dissertations in one bunch;--and no student is supposed to have even a moderate knowledge of philosophy who has not an acquaintance with that famous work, the "Critique of Pure Reason."
It is to be expected from the outset that, where so many have found so much to say, there should reign abundant differences of opinion. There are differences of opinion touching the interpretation of Kant, and touching the criticisms which may be made upon, and the development which should be given to, his doctrine. It is, of course, impossible to go into all these things here; and I shall do no more than indicate, in untechnical language and in briefest outline, what he offers us in place of the philosophy of Hume.
Kant did not try to refute, as did Reid, the doctrine, urged by Descartes and by his successors, that all those things which the mind directly perceives are to be regarded as complexes of ideas. On the contrary, he accepted it, and he has made the words "phenomenon" and "noumenon" household words in philosophy.
The world which seems to be spread out before us in s.p.a.ce and time is, he tells us, a world of things _as they are revealed to our senses and our intelligence_; it is a world of manifestations, of phenomena. What things-in-themselves are like we have no means of knowing; we know only things as they appear to us. We may, to be sure, talk of a something distinct from phenomena, a something not revealed to the senses, but thought of, a _noumenon_; but we should not forget that this is a negative conception; there is nothing in our experience that can give it a filling, for our experience is only of phenomena. The reader will find an unmistakable echo of this doctrine in Herbert Spencer"s doctrine of the "Unknowable" and its "manifestations."
Now, Berkeley had called all the things we immediately perceive _ideas_. As we have seen, he distinguished between "ideas of sense"
and "ideas of memory and imagination." Hume preferred to give to these two cla.s.ses different names--he called the first _impressions_ and the second _ideas_.
The a.s.sociations of the word "impression" are not to be mistaken.
Locke had taught that between ideas in the memory and genuine sensations there is the difference that the latter are due to the "brisk acting" of objects without us. Objects impress us, and we have sensations or impressions. To be sure, Hume, after employing the word "impression," goes on to argue that we have no evidence that there are external objects, which cause impressions. But he retains the word "impression," nevertheless, and his use of it perceptibly colors his thought.
In Kant"s distinction between phenomena and noumena we have the lineal descendant of the old distinction between the circle of our ideas and the something outside of them that causes them and of which they are supposed to give information. Hume said we have no reason to believe such a thing exists, but are impelled by our nature to believe in it.
Kant is not so much concerned to prove the nonexistence of noumena, things-in-themselves, as he is to prove that the very conception is an empty one. His reasonings seem to result in the conclusion that we can make no intelligible statement about things so cut off from our experience as noumena are supposed to be; and one would imagine that he would have felt impelled to go on to the frank declaration that we have no reason to believe in noumena at all, and had better throw away altogether so meaningless and useless a notion. But he was a conservative creature, and he did not go quite so far.
So far there is little choice between Kant and Hume. Certainly the former does not appear to have rehabilitated the external world which had suffered from the a.s.saults of his predecessors. What important difference is there between his doctrine and that of the man whose skeptical tendencies he wished to combat?
The difference is this: Descartes and Locke had accounted for our knowledge of things by maintaining that things act upon us, and make an impression or sensation--that their action, so to speak, begets ideas.
This is a very ancient doctrine as well as a very modern one; it is the doctrine that most men find reasonable even before they devote themselves to the study of philosophy. The totality of such impressions received from the external world, they are accustomed to regard as our _experience_ of external things; and they are inclined to think that any knowledge of external things not founded upon experience can hardly deserve the name of knowledge.
Now, Hume, when he cast doubt upon the existence of external things, did not, as I have said above, divest himself of the suggestions of the word "impression." He insists strenuously that all our knowledge is founded upon experience; and he holds that no experience can give us knowledge that is necessary and universal. We know things as they are revealed to us in our experience; but who can guarantee that we may not have new experiences of a quite different kind, and which flatly contradict the notions which we have so far attained of what is possible and impossible, true and untrue.
It is here that Kant takes issue with Hume. A survey of our knowledge makes clear, he thinks, that we are in the possession of a great deal of information that is not of the unsatisfactory kind that, according to Hume, all our knowledge of things must be. There, for example, are all the truths of mathematics. When we enunciate a truth regarding the relations of the lines and angles of a triangle, we are not merely unfolding in the predicate of our proposition what was implicitly contained in the subject. There are propositions that do no more than this; they are _a.n.a.lytical_, _i.e._ they merely a.n.a.lyze the subject.
Thus, when we say: Man is a rational animal, we may merely be defining the word "man"--unpacking it, so to speak. But a _synthetic_ judgment is one in which the predicate is not contained in the subject; it adds to one"s information. The mathematical truths are of this character.
So also is the truth that everything that happens must have a cause.
Do we connect things with one another in this way merely because we have had _experience_ that they are thus connected? Is it because they are _given_ to us connected in this way? That cannot be the case, Kant argues, for what is taken up as mere experienced act cannot be known as universally and necessarily true. We perceive that these things _must_ be so connected. How shall we explain this necessity?
We can only explain it, said Kant, in this way: We must a.s.sume that what is given us from without is merely the raw material of sensation, the _matter_ of our experience; and that the ordering of this matter, the arranging it into a world of phenomena, the furnishing of _form_, is the work of the mind. Thus, we must think of s.p.a.ce, time, causality, and of all other relations which obtain between the elements of our experience, as due to the nature of the mind. It perceives the world of phenomena that it does, because it _constructs_ that world.
Its knowledge of things is stable and dependable because it cannot know any phenomenon which does not conform to its laws. The water poured into a cup must take the shape of the cup; and the raw materials poured into a mind must take the form of an orderly world, spread out in s.p.a.ce and time.
Kant thought that with this turn he had placed human knowledge upon a satisfactory basis, and had, at the same time, indicated the limitations of human knowledge. If the world we perceive is a world which we make; if the forms of thought furnished by the mind have no other function than the ordering of the materials furnished by sense; then what can we say of that which may be beyond phenomena? What of _noumena_?
It seems clear that, on Kant"s principles, we ought not to be able to say anything whatever of _noumena_. To say that such may exist appears absurd. All conceivable connection between them and existing things as we know them is cut off. We cannot think of a noumenon as a _substance_, for the notions of substance and quality have been declared to be only a scheme for the ordering of phenomena. Nor can we think of one as a cause of the sensations that we unite into a world, for just the same reason. We are shut up logically to the world of phenomena, and that world of phenomena is, after all, the successor of the world of ideas advocated by Berkeley.
This is not the place to discuss at length the value of Kant"s contribution to philosophy.[3] There is something terrifying in the prodigious length at which it seems possible for men to discuss it.
Kant called his doctrine "Criticism," because it undertook to establish the nature and limits of our knowledge. By some he has been hailed as a great enlightener, and by others he has been accused of being as dogmatic in his a.s.sumptions as those whom he disapproved.
But one thing he certainly has accomplished. He has made the words "phenomena" and "noumena" familiar to us all, and he has induced a vast number of men to accept it as established fact that it is not worth while to try to extend our knowledge beyond phenomena. One sees his influence in the writings of men who differ most widely from one another.
[1] "Essay," Book IV, Chapter XI, section 7.
[2] "An Inquiry into the Human Mind," Chapter V, section 5.
[3] The reader will find a criticism of the Critical Philosophy in Chapter XV.
CHAPTER XIII
REALISM AND IDEALISM
52. REALISM.--The plain man is a realist. That is to say, he believes in a world which is not to be identified with his own ideas or those of any other mind. At the same time, as we have seen (section 12), the distinction between the mind and the world is by no means clear to him.
It is not difficult, by judicious questioning, to set his feet upon the slippery descent that shoots a man into idealism.
The vague realism of the plain man may be called _Nave_ or _Unreflective Realism_. It has been called by some _Natural Realism_, but the latter term is an unfortunate one. It is, of course, natural for the unreflective man to be unreflective, but, on the other hand, it is also natural for the reflective man to be reflective. Besides, in dubbing any doctrine "natural," we are apt to a.s.sume that doctrines contrasted with it may properly be called "unnatural" or "artificial."
It is an ancient rhetorical device, to obtain sympathy for a cause in which one may happen to be interested by giving it a taking name; but it is a device frowned upon by logic and by good sense.
One kind of realism is, then, nave realism. It is the position from which we all set out, when we begin to reflect upon the system of things. It is the position to which some try to come back, when their reflections appear to be leading them into strange or unwelcome paths.
We have seen how Thomas Reid (section 50) recoiled from the conclusions to which the reasonings of the philosophers had brought him, and tried to return to the position of the plain man. The attempt was a failure, and was necessarily a failure, for Reid tried to come back to the position of the plain man _and still be a philosopher_. He tried to live in a cloud and, nevertheless, to see clearly--a task not easy to accomplish.
It should be remarked, however, that he tried, at least, to insist that we know the external world _directly_. We may divide realists into two broad cla.s.ses, those who hold to this view, and those who maintain that we know it only indirectly and through our ideas.
The plain man belongs, of course, to the first cla.s.s, if it is just to speak of a man who says inconsistent things as being wholly in any one cla.s.s. Certainly he is willing to a.s.sert that the ground upon which he stands and the staff in his hand are perceived by him directly.
But we are compelled to recognize that there are subdivisions in this first cla.s.s of realists. Reid tried to place himself beside the plain man and failed to do so. Hamilton (section 50) tried also, and he is not to be cla.s.sed precisely either with the plain man or with Reid. He informs us that the object as it appears to us is a composite something to the building up of which the knowing mind contributes its share, the medium through which the object is perceived its share, and the object in itself its share. He suggests, by way of ill.u.s.tration, that the external object may contribute one third. This seems to make, at least, _something_ external directly known. But, on the other hand, he maintains that the mind knows immediately only what is in immediate contact with the bodily organ--with the eyes, with the hands, etc.; and he believes it knows this immediately because it is actually present in all parts of the body. And, further, in distinguishing as he does between existence "as it is in itself" and existence "as it is revealed to us," and in shutting us up to the latter, he seems to rob us even of the modic.u.m of externality that he has granted us.
I have already mentioned Herbert Spencer (section 50) as a man not without sympathy for the attempt to rehabilitate the external world.
He is very severe with the "insanities" of idealism. He is not willing even to take the first step toward it.
He writes:[1] "The postulate with which metaphysical reasoning sets out is that we are primarily conscious only of our sensations--that we certainly know we have these, and that if there be anything beyond these serving as cause for them, it can be known only by inference from them.
"I shall give much surprise to the metaphysical reader if I call in question this postulate; and the surprise will rise into astonishment if I distinctly deny it. Yet I must do this. Limiting the proposition to those epiperipheral feelings produced in us by external objects (for these are alone in question), I see no alternative but to affirm that the thing primarily known is not that a sensation has been experienced, but that there exists an outer object."
According to this, the outer object is not known through an inference; it is known directly. But do not be in haste to cla.s.s Spencer with the plain man, or with Reid. Listen to a citation once before made (section 22), but worth repeating in this connection: "When we are taught that a piece of matter, regarded by us as existing externally, cannot be really known, but that we can know only certain impressions produced on us, we are yet, by the relativity of thought, compelled to think of these in relation to a cause--the notion of a real existence which generated these impressions becomes nascent. If it be proved that every notion of a real existence which we can frame is inconsistent with itself,--that matter, however conceived by us, cannot be matter as it actually is,--our conception, though transfigured, is not destroyed: there remains the sense of reality, dissociated as far as possible from those special forms under which it was before represented in thought."
It is interesting to place the two extracts side by side. In the one, we are told that we do not know external objects by an inference from our sensations; in the other we are taught that the piece of matter which we regard as existing externally cannot be really known; that we can know only certain impressions produced on us, and must refer them to a cause; that this cause cannot be what we think it. It is difficult for the man who reads such statements not to forget that Spencer regarded himself as a realist who held to a direct knowledge of something external.
There are, as it is evident, many sorts of realists that may be gathered into the first cla.s.s mentioned above--men who, however inconsistent they may be, try, at least, to maintain that our knowledge of the external world is a direct one. And it is equally true that there are various sorts of realists that may be put into the second cla.s.s.
These men have been called _Hypothetical Realists_. In the last chapter it was pointed out that Descartes and Locke belong to this cla.s.s. Both of these men believed in an external world, but believed that its existence is a thing to be inferred.
Now, when a man has persuaded himself that the mind can know directly only its own ideas, and must infer the world which they are supposed to represent, he may conceive of that external world in three different ways.
(1) He may believe that what corresponds to his idea of a material object, for example, an apple, is in very many respects like the idea in his mind. Thus, he may believe that the odor, taste, color, hardness, etc., that he perceives directly, or as ideas, have corresponding to them real external odor, taste, color, hardness, etc.
It is not easy for a man to hold to this position, for a very little reflection seems to make it untenable; but it is theoretically possible for one to take it, and probably many persons have inclined to the view when they have first been tempted to believe that the mind perceives directly only its ideas.
(2) He may believe that such things as colors, tastes, and odors cannot be qualities of external bodies at all, but are only effects, produced upon our minds by something very different in kind. We seem to perceive bodies, he may argue, to be colored, to have taste, and to be odorous; but what we thus perceive is not the external thing; the external thing that produces these appearances cannot be regarded as having anything more than "solidity, extension, figure, motion or rest, and number." Thus did Locke reason. To him the external world as it really exists, is, so to speak, a paler copy of the external world as we seem to perceive it. It is a world with fewer qualities, but, still, a world with qualities of some kind.
(3) But one may go farther than this. One may say: How can I know that even the extension, number, and motion of the things which I directly perceive have corresponding to them extension, number, and motion, in an outer world? If what is not colored can cause me to perceive color, why may not that which is not extended cause me to perceive extension?
And, moved by such reflections, one may maintain that there exists outside of us that which we can only characterize as an Unknown Cause, a Reality which we cannot more nearly define.
This last position resembles very closely one side of Spencer"s doctrine--that represented in the last of the two citations, as the reader can easily see. It is the position of the follower of Immanuel Kant who has not yet repudiated the noumenon or thing-in-itself discussed in the last chapter (section 51).
I am not concerned to defend any one of the varieties of Direct or of Hypothetical Realism portrayed above. But I wish to point out that they all have some sort of claim to the t.i.tle _Realism_, and to remind the reader that, when we call a man a realist, we do not do very much in the way of defining his position. I may add that the account of the external world contained in Chapter IV is a sort of realism also.