The method of our own system is toto genere distinct from these two opposite misconceptions, for we start neither from the object nor from the subject, but from the idea, as the first fact of consciousness. Its first essential, fundamental form is the antithesis of subject and object. The form of the object again is the principle of sufficient reason in its various forms. Each of these reigns so absolutely in its own class of ideas that, as we have seen, when the special form of the principle of sufficient reason which governs any class of ideas is known, the nature of the whole class is known also: for the whole class, as idea, is no more than this form of the principle of sufficient reason itself; so that time itself is nothing but the principle of existence in it, i. e., succession; space is nothing but the principle of existence in it, i. e., position; matter is nothing but causality; the concept (as will appear immediately) is nothing but relation to a ground of knowledge. This thorough and consistent relativity of the world as idea, both according to its universal form (subject and object), and according to the form which is subordinate to this (the principle of sufficient reason) warns us, as we said before, to seek the inner nature of the world in an aspect of it which is quite different and quite distinct from the idea; and in the next book we shall find this in a fact which is just as immediate to every living being as the idea.
But we must first consider that class of ideas which belongs to man alone. The matter of these is the concept, and the subjective correlative is reason, just as the subjective correlative of the ideas we have already considered was understanding and sensibility, which are also to be attributed to all the lower animals.11
§ 8. As from the direct light of the sun to the borrowed light of the moon, we pass from the immediate idea of perception, which stands by itself and is its own warrant, to reflection, to the abstract, discursive concepts of the reason, which obtain their whole content from knowledge of perception, and in relation to it. As long as we continue simply to perceive, all is clear, firm, and certain. There are neither questions nor doubts nor errors; we desire to go no further, can go no further; we find rest in perceiving, and satisfaction in the present. Perception suffices for itself, and therefore what springs purely from it, and remains true to it, for example, a genuine work of art, can never be false, nor can it be discredited through the lapse of time, for it does not present an opinion but the thing itself. But with abstract knowledge, with reason, doubt and error appear in the theoretical, care and sorrow in the practical. In the idea of perception, illusion may at moments take the place of the real; but in the sphere of abstract thought, error may reign for a thousand years, impose its yoke upon whole nations, extend to the noblest impulses of humanity, and, by the help of its slaves and its dupes, may chain and fetter those whom it cannot deceive. It is the enemy against which the wisest men of all times have waged unequal war, and only what they have won from it has become the possession of mankind. Therefore it is well to draw attention to it at once, as we already tread the ground to which its province belongs. It has often been said that we ought to follow truth even although no utility can be seen in it, because it may have indirect utility which may appear when it is least expected; and I would add to this, that we ought to be just as anxious to discover and to root out all error even when no harm is anticipated from it, because its mischief may be very indirect, and may suddenly appear when we do not expect it, for all error has poison at its heart. If it is mind, if it is knowledge, that makes man the lord of creation, there can be no such thing as harmless error, still less venerable and holy error. And for the consolation of those who in any way and at any time may have devoted strength and life to the noble and hard battle against error, I cannot refrain from adding that, so long as truth is absent, error will have free play, as owls and bats in the night; but sooner would we expect to see the owls and the bats drive back the sun in the eastern heavens, than that any truth which has once been known and distinctly and fully expressed, can ever again be so utterly vanquished and overcome that the old error shall once more reign undisturbed over its wide kingdom. This is the power of truth; its conquest is slow and laborious, but if once the victory be gained it can never be wrested back again.
Besides the ideas we have as yet considered, which, according to their construction, could be referred to time, space, and matter, if we consider them with reference to the object, or to pure sensibility and understanding (i. e., knowledge of causality), if we consider them with reference to the subject, another faculty of knowledge has appeared in man alone of all earthly creatures, an entirely new consciousness, which, with very appropriate and significant exactness, is called reflection. For it is in fact derived from the knowledge of perception, and is a reflected appearance of it. But it has assumed a nature fundamentally different. The forms of perception do not affect it, and even the principle of sufficient reason which reigns over all objects has an entirely different aspect with regard to it. It is just this new, more highly endowed, consciousness, this abstract reflex of all that belongs to perception in that conception of the reason which has nothing to do with perception, that gives to man that thoughtfulness which distinguishes his consciousness so entirely from that of the lower animals, and through which his whole behaviour upon earth is so different from that of his irrational fellow-creatures. He far surpasses them in power and also in suffering. They live in the present alone, he lives also in the future and the past. They satisfy the needs of the moment, he provides by the most ingenious preparations for the future, yea for days that he shall never see. They are entirely dependent on the impression of the moment, on the effect of the perceptible motive; he is determined by abstract conceptions independent of the present. Therefore he follows predetermined plans, he acts from maxims, without reference to his surroundings or the accidental impression of the moment. Thus, for example, he can make with composure deliberate preparations for his own death, he can dissemble past finding out, and can carry his secret with him to the grave; lastly, he has an actual choice between several motives; for only in the abstract can such motives, present together in consciousness, afford the knowledge with regard to themselves, that the one excludes the other, and can thus measure themselves against each other with reference to their power over the will. The motive that overcomes, in that it decides the question at issue, is the deliberate determinant of the will, and is a sure indication of its character. The brute, on the other hand, is determined by the present impression; only the fear of present compulsion can constrain its desires, until at last this fear has become custom, and as such continues to determine it; this is called training. The brute feels and perceives; man, in addition to this, thinks and knows: both will. The brute expresses its feelings and dispositions by gestures and sounds; man communicates his thought to others, or, if he wishes, he conceals it, by means of speech. Speech is the first production, and also the necessary organ of his reason. Therefore in Greek and Italian, speech and reason are expressed by the same word; ὁ λογος, il discorso. Vernunft is derived from vernehmen, which is not a synonym for the verb to hear, but signifies the consciousness of the meaning of thoughts communicated in words. It is by the help of language alone that reason accomplishes its most important achievements, – the united action of several individuals, the planned co-operation of many thousands, civilisation, the state; also science, the storing up of experience, the uniting of common properties in one concept, the communication of truth, the spread of error, thoughts and poems, dogmas and superstitions. The brute first knows death when it dies, but man draws consciously nearer to it every hour that he lives; and this makes life at times a questionable good even to him who has not recognised this character of constant annihilation in the whole of life. Principally on this account man has philosophies and religions, though it is uncertain whether the qualities we admire most in his conduct, voluntary rectitude and nobility of feeling, were ever the fruit of either of them. As results which certainly belong only to them, and as productions of reason in this sphere, we may refer to the marvellous and monstrous opinions of philosophers of various schools, and the extraordinary and sometimes cruel customs of the priests of different religions.
It is the universal opinion of all times and of all nations that these manifold and far-reaching achievements spring from a common principle, from that peculiar intellectual power which belongs distinctively to man and which has been called reason, ὁ λογος, το λογιστικον, το λογιμον, ratio. Besides this, no one finds any difficulty in recognising the manifestations of this faculty, and in saying what is rational and what is irrational, where reason appears as distinguished from the other faculties and qualities of man, or lastly, in pointing out what, on account of the want of reason, we must never expect even from the most sensible brute. The philosophers of all ages may be said to be on the whole at one about this general knowledge of reason, and they have also given prominence to several very important manifestations of it; such as, the control of the emotions and passions, the capacity for drawing conclusions and formulating general principles, even such as are true prior to all experience, and so forth. Still all their explanations of the peculiar nature of reason are wavering, not clearly defined, discursive, without unity and concentration; now laying stress on one manifestation, now on another, and therefore often at variance with each other. Besides this, many start from the opposition between reason and revelation, a distinction which is unknown to philosophy, and which only increases confusion. It is very remarkable that up till now no philosopher has referred these manifold expressions of reason to one simple function which would be recognised in them all, from which they would all be explained, and which would therefore constitute the real inner nature of reason. It is true that the excellent Locke in the “Essay on the Human Understanding” (Book II., ch. xi., §§ 10 and 11), very rightly refers to general concepts as the characteristic which distinguishes man from the brutes, and Leibnitz quotes this with full approval in the “Nouveaux Essais sur l'Entendement Humaine” (Book II., ch. xi., §§ 10 and 11.) But when Locke (in Book IV., ch. xvii., §§ 2 and 3) comes to the special explanation of reason he entirely loses sight of this simple, primary characteristic, and he also falls into a wavering, undetermined, incomplete account of mangled and derivative manifestations of it. Leibnitz also, in the corresponding part of his work, behaves in a similar manner, only with more confusion and indistinctness. In the Appendix, I have fully considered how Kant confused and falsified the conception of the nature of reason. But whoever will take the trouble to go through in this reference the mass of philosophical writing which has appeared since Kant, will find out, that just as the faults of princes must be expiated by whole nations, the errors of great minds extend their influence over whole generations, and even over centuries; they grow and propagate themselves, and finally degenerate into monstrosities. All this arises from the fact that, as Berkeley says, “Few men think; yet all will have opinions.”
The understanding has only one function – immediate knowledge of the relation of cause and effect. Yet the perception of the real world, and all common sense, sagacity, and inventiveness, however multifarious their applications may be, are quite clearly seen to be nothing more than manifestations of that one function. So also the reason has one function; and from it all the manifestations of reason we have mentioned, which distinguish the life of man from that of the brutes, may easily be explained. The application or the non-application of this function is all that is meant by what men have everywhere and always called rational and irrational.12
§ 9. Concepts form a distinct class of ideas, existing only in the mind of man, and entirely different from the ideas of perception which we have considered up till now. We can therefore never attain to a sensuous and, properly speaking, evident knowledge of their nature, but only to a knowledge which is abstract and discursive. It would, therefore, be absurd to demand that they should be verified in experience, if by experience is meant the real external world, which consists of ideas of perception, or that they should be brought before the eyes or the imagination like objects of perception. They can only be thought, not perceived, and only the effects which men accomplish through them are properly objects of experience. Such effects are language, preconceived and planned action and science, and all that results from these. Speech, as an object of outer experience, is obviously nothing more than a very complete telegraph, which communicates arbitrary signs with the greatest rapidity and the finest distinctions of difference. But what do these signs mean? How are they interpreted? When some one speaks, do we at once translate his words into pictures of the fancy, which instantaneously flash upon us, arrange and link themselves together, and assume form and colour according to the words that are poured forth, and their grammatical inflections? What a tumult there would be in our brains while we listened to a speech, or to the reading of a book? But what actually happens is not this at all. The meaning of a speech is, as a rule, immediately grasped, accurately and distinctly taken in, without the imagination being brought into play. It is reason which speaks to reason, keeping within its own province. It communicates and receives abstract conceptions, ideas that cannot be presented in perceptions, which are framed once for all, and are relatively few in number, but which yet encompass, contain, and represent all the innumerable objects of the actual world. This itself is sufficient to prove that the lower animals can never learn to speak or comprehend, although they have the organs of speech and ideas of perception in common with us. But because words represent this perfectly distinct class of ideas, whose subjective correlative is reason, they are without sense and meaning for the brutes. Thus language, like every other manifestation which we ascribe to reason, and like everything which distinguishes man from the brutes, is to be explained from this as its one simple source – conceptions, abstract ideas which cannot be presented in perception, but are general, and have no individual existence in space and time. Only in single cases do we pass from the conception to the perception, do we construct images as representatives of concepts in perception, to which, however, they are never adequate. These cases are fully discussed in the essay on the principle of sufficient reason, § 28, and therefore I shall not repeat my explanation here. It may be compared, however, with what is said by Hume in the twelfth of his “Philosophical Essays,” p. 244, and by Herder in the “Metacritik,” pt. i. p. 274 (an otherwise worthless book). The Platonic idea, the possibility of which depends upon the union of imagination and reason, is the principal subject of the third book of this work.
Although concepts are fundamentally different from ideas of perception, they stand in a necessary relation to them, without which they would be nothing. This relation therefore constitutes the whole nature and existence of concepts. Reflection is the necessary copy or repetition of the originally presented world of perception, but it is a special kind of copy in an entirely different material. Thus concepts may quite properly be called ideas of ideas. The principle of sufficient reason has here also a special form. Now we have seen that the form under which the principle of sufficient reason appears in a class of ideas always constitutes and exhausts the whole nature of the class, so far as it consists of ideas, so that time is throughout succession, and nothing more; space is throughout position, and nothing more; matter is throughout causation, and nothing more. In the same way the whole nature of concepts, or the class of abstract ideas, consists simply in the relation which the principle of sufficient reason expresses in them; and as this is the relation to the ground of knowledge, the whole nature of the abstract idea is simply and solely its relation to another idea, which is its ground of knowledge. This, indeed, may, in the first instance, be a concept, an abstract idea, and this again may have only a similar abstract ground of knowledge; but the chain of grounds of knowledge does not extend ad infinitum; it must end at last in a concept which has its ground in knowledge of perception; for the whole world of reflection rests on the world of perception as its ground of knowledge. Hence the class of abstract ideas is in this respect distinguished from other classes; in the latter the principle of sufficient reason always demands merely a relation to another idea of the same class, but in the case of abstract ideas, it at last demands a relation to an idea of another class.
Those concepts which, as has just been pointed out, are not immediately related to the world of perception, but only through the medium of one, or it may be several other concepts, have been called by preference abstracta, and those which have their ground immediately in the world of perception have been called concreta. But this last name is only loosely applicable to the concepts denoted by it, for they are always merely abstracta, and not ideas of perception. These names, which have originated in a very dim consciousness of the distinctions they imply, may yet, with this explanation, be retained. As examples of the first kind of concepts, i. e., abstracta in the fullest sense, we may take “relation,” “virtue,” “investigation,” “beginning,” and so on. As examples of the second kind, loosely called concreta, we may take such concepts as “man,” “stone,” “horse,” &c. If it were not a somewhat too pictorial and therefore absurd simile, we might very appropriately call the latter the ground floor, and the former the upper stories of the building of reflection.13
It is not, as is commonly supposed, an essential characteristic of a concept that it should contain much under it, that is to say, that many ideas of perception, or it may be other abstract ideas, should stand to it in the relation of its ground of knowledge, i. e., be thought through it. This is merely a derived and secondary characteristic, and, as a matter of fact, does not always exist, though it must always exist potentially. This characteristic arises from the fact that a concept is an idea of an idea, i. e., its whole nature consists in its relation to another idea; but as it is not this idea itself, which is generally an idea of perception and therefore belongs to quite a different class, the latter may have temporal, spacial, and other determinations, and in general many relations which are not thought along with it in the concept. Thus we see that several ideas which are different in unessential particulars may be thought by means of one concept, i. e., may be brought under it. Yet this power of embracing several things is not an essential but merely an accidental characteristic of the concept. There may be concepts through which only one real object is thought, but which are nevertheless abstract and general, by no means capable of presentation individually and as perceptions. Such, for example, is the conception which any one may have of a particular town which he only knows from geography; although only this one town is thought under it, it might yet be applied to several towns differing in certain respects. We see then that a concept is not general because of being abstracted from several objects; but conversely, because generality, that is to say, non-determination of the particular, belongs to the concept as an abstract idea of the reason, different things can be thought by means of the same one.
It follows from what has been said that every concept, just because it is abstract and incapable of presentation in perception, and is therefore not a completely determined idea, has what is called extension or sphere, even in the case in which only one real object exists that corresponds to it. Now we always find that the sphere of one concept has something in common with the sphere of other concepts. That is to say, part of what is thought under one concept is the same as what is thought under other concepts; and conversely, part of what is thought under these concepts is the same as what is thought under the first; although, if they are really different concepts, each of them, or at least one of them, contains something which the other does not contain; this is the relation in which every subject stands to its predicate. The recognition of this relation is called judgment. The representation of these spheres by means of figures in space, is an exceedingly happy idea. It first occurred to Gottfried Plouquet, who used squares for the purpose. Lambert, although later than him, used only lines, which he placed under each other. Euler carried out the idea completely with circles. Upon what this complete analogy between the relations of concepts, and those of figures in space, ultimately rests, I am unable to say. It is, however, a very fortunate circumstance for logic that all the relations of concepts, according to their possibility, i. e., a priori, may be made plain in perception by the use of such figures, in the following way: —
(1.) The spheres of two concepts coincide: for example the concept of necessity and the concept of following from given grounds, in the same way the concepts of Ruminantia and Bisulca (ruminating and cloven-hoofed animals), also those of vertebrate and red-blooded animals (although there might be some doubt about this on account of the annelida): they are convertible concepts. Such concepts are represented by a single circle which stands for either of them.
(2.) The sphere of one concept includes that of the other.
(3.) A sphere includes two or more spheres which exclude each other and fill it.
(4.) Two spheres include each a part of the other.
(5.) Two spheres lie in a third, but do not fill it.
This last case applies to all concepts whose spheres have nothing immediately in common, for there is always a third sphere, often a much wider one, which includes both.
To these cases all combinations of concepts may be referred, and from them the entire doctrine of the judgment, its conversion, contraposition, equipollence, disjunction (this according to the third figure) may be deduced. From these also may be derived the properties of the judgment, upon which Kant based his pretended categories of the understanding, with the exception however of the hypothetical form, which is not a combination of concepts, but of judgments. A full account is given in the Appendix of “Modality,” and indeed of every property of judgments on which the categories are founded.
With regard to the possible combinations of concepts which we have given, it has only further to be remarked that they may also be combined with each other in many ways. For example, the fourth figure with the second. Only if one sphere, which partly or wholly contains another, is itself contained in a third sphere, do these together exemplify the syllogism in the first figure, i. e., that combination of judgments, by means of which it is known that a concept which is partly or wholly contained in another concept, is also contained in a third concept, which again contains the first: and also, conversely, the negation; the pictorial representation of which can, of course, only be two connected spheres which do not lie within a third sphere. If many spheres are brought together in this way we get a long train of syllogisms. This schematism of concepts, which has already been fairly well explained in more than one textbook, may be used as the foundation of the doctrine of the judgment, and indeed of the whole syllogistic theory, and in this way the treatment of both becomes very easy and simple. Because, through it, all syllogistic rules may be seen in their origin, and may be deduced and explained. It is not necessary, however, to load the memory with these rules, as logic is never of practical use, but has only a theoretical interest for philosophy. For although it may be said that logic is related to rational thinking as thorough-bass is to music, or less exactly, as ethics is to virtue, or æsthetics to art; we must yet remember that no one ever became an artist by the study of æsthetics; that a noble character was never formed by the study of ethics; that long before Rameau, men composed correctly and beautifully, and that we do not need to know thorough-bass in order to detect discords: and just as little do we need to know logic in order to avoid being misled by fallacies. Yet it must be conceded that thorough-bass is of the greatest use in the practice of musical composition, although it may not be necessary for the understanding of it; and indeed æsthetics and even ethics, though in a much less degree, and for the most part negatively, may be of some use in practice, so that we cannot deny them all practical worth, but of logic even this much cannot be conceded. It is nothing more than the knowledge in the abstract of what every one knows in the concrete. Therefore we call in the aid of logical rules, just as little to enable us to construct a correct argument as to prevent us from consenting to a false one, and the most learned logician lays aside the rules of logic altogether in his actual thought. This may be explained in the following way. Every science is a system of general and therefore abstract truths, laws, and rules with reference to a special class of objects. The individual case coming under these laws is determined in accordance with this general knowledge, which is valid once for all; because such application of the general principle is far easier than the exhaustive investigation of the particular case; for the general abstract knowledge which has once been obtained is always more within our reach than the empirical investigation of the particular case. With logic, however, it is just the other way. It is the general knowledge of the mode of procedure of the reason expressed in the form of rules. It is reached by the introspection of reason, and by abstraction from all content. But this mode of procedure is necessary and essential to reason, so that it will never depart from it if left to itself. It is, therefore, easier and surer to let it proceed itself according to its nature in each particular case, than to present to it the knowledge abstracted from this procedure in the form of a foreign and externally given law. It is easier, because, while in the case of all other sciences, the general rule is more within our reach than the investigation of the particular case taken by itself; with the use of reason, on the contrary, its necessary procedure in a given case is always more within our reach than the general rule abstracted from it; for that which thinks in us is reason itself. It is surer, because a mistake may more easily occur in such abstract knowledge, or in its application, than that a process of reason should take place which would run contrary to its essence and nature. Hence arises the remarkable fact, that while in other sciences the particular case is always proved by the rule, in logic, on the contrary, the rule must always be proved from the particular case; and even the most practised logician, if he remark that in some particular case he concludes otherwise than the rule prescribes, will always expect to find a mistake in the rule rather than in his own conclusion. To desire to make practical use of logic means, therefore, to desire to derive with unspeakable trouble, from general rules, that which is immediately known with the greatest certainty in the particular case. It is just as if a man were to consult mechanics as to the motion of his body, and physiology as to his digestion; and whoever has learnt logic for practical purposes is like him who would teach a beaver to make its own dam. Logic is, therefore, without practical utility; but it must nevertheless be retained, because it has philosophical interest as the special knowledge of the organisation and action of reason. It is rightly regarded as a definite, self-subsisting, self-contained, complete, and thoroughly safe discipline; to be treated scientifically for itself alone and independently of everything else, and therefore to be studied at the universities. But it has its real value, in relation to philosophy as a whole, in the inquiry into the nature of knowledge, and indeed of rational and abstract knowledge. Therefore the exposition of logic should not have so much the form of a practical science, should not contain merely naked arbitrary rules for the correct formation of the judgment, the syllogism, &c., but should rather be directed to the knowledge of the nature of reason and the concept, and to the detailed investigation of the principle of sufficient reason of knowing. For logic is only a paraphrase of this principle, and, more exactly, only of that exemplification of it in which the ground that gives truth to the judgment is neither empirical nor metaphysical, but logical or metalogical. Besides the principle of sufficient reason of knowing, it is necessary to take account of the three remaining fundamental laws of thought, or judgments of metalogical truth, so nearly related to it; and out of these the whole science of reason grows. The nature of thought proper, that is to say, of the judgment and the syllogism, must be exhibited in the combination of the spheres of concepts, according to the analogy of the special schema, in the way shown above; and from all this the rules of the judgment and the syllogism are to be deduced by construction. The only practical use we can make of logic is in a debate, when we can convict our antagonist of his intentional fallacies, rather than of his actual mistakes, by giving them their technical names. By thus throwing into the background the practical aim of logic, and bringing out its connection with the whole scheme of philosophy as one of its chapters, we do not think that we shall make the study of it less prevalent than it is just now. For at the present day every one who does not wish to remain uncultured, and to be numbered with the ignorant and incompetent multitude, must study speculative philosophy. For the nineteenth century is a philosophical age, though by this we do not mean either that it has philosophy, or that philosophy governs it, but rather that it is ripe for philosophy, and, therefore, stands in need of it. This is a sign of a high degree of civilisation, and indeed, is a definite stage in the culture of the ages.14