As from the direct light of the sun to the borrowed reflected light of the moon, so do we pass from the immediate representation of perception, which stands by itself and is its own warrant, to reflection, to the abstract, discursive concepts of reason (Vernunft), which have their whole content only from that knowledge of perception, and in relation to it. As long as our attitude is one of pure perception, all is clear, firm, and certain. For there are neither questions nor doubts nor errors; we do not wish to go farther, we cannot go farther; we have rest in perceiving, and satisfaction in the present moment. Perception by itself is enough; therefore what has sprung purely from it and has remained true to it, like the genuine work of art, can never be false, nor can it be refuted through any passing of time, for it gives us not opinion, but the thing itself. With abstract knowledge, with the faculty of reason, doubt and error have appeared in the theoretical, care and remorse in the practical. If in the representation of perception illusion does at moments distort reality, then in the representation of the abstract error can reign for thousands of years, impose its iron yoke on whole nations, stifle the noblest impulses of mankind; through its slaves and dupes it can enchain even the man it cannot deceive. It is the enemy against which the wisest minds of all times have kept up an unequal struggle, and only what these have won from it has become the property of mankind. Therefore it is a good thing to draw attention to it at once, since we are now treading the ground where its province lies. Although it has often been said that we ought to pursue truth, even when no use for it can be seen, since its use may be indirect and appear when not expected, I find I must add here that we should be just as anxious to discover and eradicate every error, even when no harm from it can be seen, because this harm may be very indirect, and appear one day when not expected; for every error carries a poison within itself. If it is the mind, if it is knowledge, that makes man lord of the earth, then no errors are harmless, still less venerable and holy. And for the consolation of those who devote their strength and life in any way or concern to the noble and difficult struggle against error, I cannot refrain from adding here that, so long as truth does not exist, error can play its game, just as owls and bats do at night. But we may sooner expect that owls and bats will drive the sun back into the east than that any truth that is known and expressed clearly and fully will again be supplanted, so that the old error may once more occupy its extensive position undisturbed. This is the power of truth, whose conquest is difficult and laborious; but when victory for it is once gained, it can never be wrested away again.
Besides the representations so far considered, namely those which according to their construction could be referred to time, space, and matter, if we see them with reference to the object, or to pure sensibility and understanding (i.e., knowledge of causality) if we see them with reference to the subject, yet another faculty of knowledge has appeared in man alone of all the inhabitants of the earth; an entirely new consciousness has arisen, which with very appropriate and significant accuracy is called reflection. For it is in fact a reflected appearance, a thing derived from this knowledge of perception, yet it has assumed a fundamentally different nature and character. It is not acquainted with the forms of perception, and in its regard even the principle of sufficient reason, which rules over every object, has an entirely different form. It is only this new consciousness at a higher potential, this abstract reflex of everything intuitive in the non-perceptive conception of reason, that endows man with that thoughtfulness which so completely distinguishes his consciousness from that of the animal, and through which his whole behaviour on earth turns out so differently from that of his irrational brothers. He far surpasses them in power and in suffering. They live in the present alone; he lives at the same time in the future and the past. They satisfy the need of the moment; he provides by the most ingenious preparations for his future, nay, even for times that he cannot live to see. They are given up entirely to the impression of the moment, to the effect of the motive of perception; he is determined by abstract concepts independent of the present moment. He therefore carries out considered plans, or acts in accordance with maxims, without regard to his surroundings, and to the accidental impressions of the moment. Thus, for example, he can with composure take cunning measures for his own death, dissemble to the point of inscrutableness, and take his secret with him to the grave. Finally, he has an actual choice between several motives, for only in abstracto can such motives, simultaneously present in consciousness, afford knowledge with regard to themselves that the one excludes the other, and thus measure against one another their power over the will. Accordingly, the motive that prevails, in that it decides the matter, is the deliberate decision of the will, and it makes known as a sure indication the character of the will. The animal, on the contrary, is determined by the present impression; only the fear of present compulsion can restrain his desires, until at last this fear has become custom, and as such determines him; this is training. The animal feels and perceives; man, in addition, thinks and knows; both will. The animal communicates his feelings and moods by gesture and sound; man communicates thought to another, or conceals it from him, by language. Speech is the first product and the necessary instrument of his faculty of reason. Therefore in Greek and Italian speech and reason are expressed by the same word, ὁ λόγoς, il discorso. Vernunft (reason) comes from vernehmen, which is not synonymous with hearing, but signifies the awareness of ideas communicated by words. Only by the aid of language does reason bring about its most important achievements, namely the harmonious and consistent action of several individuals, the planned cooperation of many thousands, civilization, the State; and then, science, the storing up of previous experience, the summarizing into one concept of what is common, the communication of truth, the spreading of error, thoughts and poems, dogmas and superstitions. The animal learns to know death only when he dies, but man consciously draws every hour nearer his death; and at times this makes life a precarious business, even to the man who has not already recognized this character of constant annihilation in the whole of life itself. Mainly on this account, man has philosophies and religions, though it is doubtful whether that which we rightly esteem above all else in his conduct, namely voluntary rectitude and nobility of feeling, have ever been the fruit of them. On the other hand, there are on this path, as certain creations belonging to them alone and as productions of reason, the strangest and oddest opinions of the philosophers of different schools, and the most extraordinary, and sometimes even cruel, customs of the priests of different religions.
It is the unanimous opinion of all times and of all nations that all these manifestations, so manifold and so far-reaching, spring from a common principle, from that special power of the mind which man possesses as distinct from the animal, and which has been called Vernunft, reason, ὁ λόγoς, τὸ λoγιϭτιϰόν, τὸ λόγιϰoν, ratio. All men also know quite well how to recognize the manifestations of this faculty, and to say what is rational and what is irrational, where reason appears in contrast to man’s other faculties and qualities, and finally what can never be expected even from the cleverest animal, on account of its lack of this faculty. The philosophers of all times speak on the whole with one voice about this universal knowledge of reason, and moreover stress some particularly important manifestations of it, such as the control of the emotions and passions, the capacity to make conclusions and to lay down general principles, even those that are certain prior to all experience, and so on. Nevertheless, all their explanations of the real nature of reason are irresolute, vague, not sharply defined, diffuse, without unity or a central point, stressing one or another manifestation, and hence often at variance among themselves. Besides this, many start from the contrast between reason and revelation, a contrast wholly foreign to philosophy, and serving only to add to the confusion. It is very remarkable that hitherto no philosopher has referred all these manifold expressions of reason strictly to one simple function which could be recognized in all of them, from which they could all be explained, and which would accordingly constitute the real inner nature of reason. It is true that the eminent Locke in his Essay on the Human Understanding (Book II, chap. xi, §§ 10 and 11) very rightly states that abstract, universal concepts are the characteristic that distinguishes animal from man, and that Leibniz in complete agreement repeats this in the Nouveaux essais sur l’entendement humain (Book II, chap. xi, §§ 10 and 11). But when Locke (Book IV, chap. xvii, § § 2 and 3) comes to the real explanation of reason, he entirely loses sight of that simple main characteristic, and also falls into an irresolute, indefinite, incomplete account of piecemeal and derivative manifestations of it. In the corresponding passage of his work, Leibniz also behaves in just the same way, only with more confusion and vagueness. In the Appendix I have discussed in detail how much Kant confused and falsified the conception of the nature of reason. But he who will take the trouble to go through in this respect the mass of philosophical writings that have appeared since Kant, will recognize that, just as the mistakes of princes are expiated by whole nations, so do the errors of great minds extend their unwholesome influence over whole generations, centuries even, growing and propagating, and finally degenerating into monstrosities. All this can be deduced from the fact that, as Berkeley says, “Few men think; yet all will have opinions.” 25
The understanding has one function alone, namely immediate knowledge of the relation of cause and effect; and perception of the actual world, as well as all sagacity, good sense, and the inventive gift, however manifold their application may be, are quite obviously nothing but manifestations of that simple function. Reason also has one function, the formation of the concept, and from this single function are explained very easily and automatically all those phenomena, previously mentioned, that distinguish man’s life from that of the animal. Everything that has been called rational or irrational everywhere and always points to the application or non-application of that function.26