It must be *possible* for the *I think* to accompany all my representations: for otherwise something would be represented within me that could not be thought at all, in other words, the representation would either be impossible, or at least would be nothing to me. That representation which can be given prior to all thought is called *intuition*, and all the manifold of intuition has, therefore, a necessary relation to the *I think* in the same subject in which this manifold of intuition is found. This representation (the *I think*), however, is an act of *spontaneity*, that is, it cannot be considered as belonging to sensibility. I call it *pure apperception*, in order to distinguish it from empirical apperception, as also from original apperception, because it is that self-consciousness which, by producing the representations, *I think* (which must be capable of accompanying all other representations, and which is one and the same in all consciousness), cannot itself be accompanied by any further representations. I also call the unity of apperception the *transcendental* unity of self-consciousness, in order to indicate that *a priori* knowledge can be obtained from it. For the manifold representations given in an intuition would not one and all be *my* representations, if they did not all belong to one self-consciousness. What I mean is that, as my representations (even though I am not conscious of them as that), they must conform to the condition under which alone they *can* stand together in one universal self-consciousness, because otherwise they would not one and all belong to me. From this original combination much can be inferred.The thoroughgoing identity of the apperception of a manifold that is given in intuition contains a synthesis of representations, and is possible only through the consciousness of this synthesis. For the empirical consciousness which accompanies different representations is itself dispersed and without reference to the identity of the subject. Such a reference comes about, not simply through my accompanying every representation with consciousness, but through my *adding* one representation to another and being conscious of the synthesis of them. Only because I am able to combine a manifold of given representations *in one consciousness* is it possible for me to represent to myself the *identity of the consciousness in these representations*, that is, only under the presupposition of some *synthetic* unity of apperception is the *analytic* unity of apperception possible. The thought that the representations given in intuition belong one and all *to me*, is therefore the same as the thought that I unite them in one self-consciousness, or can at least do so; and although that thought itself is not yet the consciousness of the synthesis of representations, it nevertheless presupposes the possibility of this synthesis. In other words, it is only because I am able to comprehend the manifold of representations in one consciousness that I call them one and all *my* representations. For otherwise I should have as many-coloured and varied a self as I have representations of which I am conscious. Synthetic unity of the manifold of intuitions, as given *a priori*, is thus the ground of the identity of apperception itself, which precedes *a priori* all *my* determinate thought. Combination, however, does not lie in the objects, and cannot be borrowed from them by perception and thus first be taken into the understanding. It is, rather, solely an act of the understanding, which itself is nothing but the faculty of combining *a priori* and of bringing the manifold of given representations under the unity of apperception; and the principle of this unity is, in fact, the supreme principle of all human knowledge.—from_Critique of Pure Reason_. Translated, edited, and with an Introduction by Marcus Weigelt, based on the translation by Max Müller, pp. 124-128

~ Immanuel Kant

It is true, no doubt, that this principle of the necessary unity of apperception is itself an identical and therefore an analytic proposition; but it shows, nevertheless, the necessity of a synthesis of the manifold given in an intuition, a synthesis without which it would be impossible to think the thoroughgoing identity of self-consciousness. For through the *I*, as a simple representation, nothing manifold is given; only in intuition, which is distinct from this representation, can a manifold be given, and then, through *combination*, be thought in one consciousness. An understanding in which through self-consciousness all the manifold would be given at the same time would be one that *intuits*; our understanding can do nothing but *think*, and must seek intuition in the senses. I am conscious, therefore, of the identical self with respect to the manifold of the representations that are given to me in an intuition, because I call them one and all *my* representations, as constituting *one* intuition. This means that I am conscious *a priori* of a necessary synthesis of them, which is called the original synthetic unity of apperception, and under which all representations given to me must stand, but under which they must also be brought by means of a synthesis.”—from_Critique of Pure Reason_. Translated, edited, and with an Introduction by Marcus Weigelt, based on the translation by Max Müller, pp. 128-129

~ Immanuel Kant

In consequence of the inevitably scattered and fragmentary nature of our thinking, which has been mentioned, and of the mixing together of the most heterogeneous representations thus brought about and inherent even in the noblest human mind, we really possess only *half a consciousness*. With this we grope about in the labyrinth of our life and in the obscurity of our investigations; bright moments illuminate our path like flashes of lighting. But what is to be expected generally from heads of which even the wisest is every night the playground of the strangest and most senseless dreams, and has to take up its meditations again on emerging from these dreams? Obviously a consciousness subject to such great limitations is little fitted to explore and fathom the riddle of the world; and to beings of a higher order, whose intellect did not have time as its form, and whose thinking therefore had true completeness and unity, such an endeavor would necessarily appear strange and pitiable. In fact, it is a wonder that we are not completely confused by the extremely heterogeneous mixture of fragments of representations and of ideas of every kind which are constantly crossing one another in our heads, but that we are always able to find our way again, and to adapt and adjust everything. Obviously there must exist a simple thread on which everything is arranged side by side: but what is this? Memory alone is not enough, since it has essential limitations of which I shall shortly speak; moreover, it is extremely imperfect and treacherous. The *logical ego*, or even the *transcendental synthetic unity of apperception*, are expressions and explanations that will not readily serve to make the matter comprehensible; on the contrary, it will occur to many that“Your wards are deftly wrought, but drive no bolts asunder.”Kant’s proposition: “The *I think* must accompany all our representations ,” is insufficient; for the “I” is an unknown quantity, in other words, it is itself a mystery and a secret. What gives unity and sequence to consciousness, since by pervading all the representations of consciousness, it is its substratum, its permanent supporter, cannot itself be conditioned by consciousness, and therefore cannot be a representation. On the contrary, it must be the *prius* of consciousness, and the root of the tree of which consciousness is the fruit. This, I say, is the *will*; it alone is unalterable and absolutely identical, and has brought forth consciousness for its own ends. It is therefore the will that gives unity and holds all its representations and ideas together, accompanying them, as it were, like a continuous ground-bass. Without it the intellect would have no more unity of consciousness than has a mirror, in which now one thing now another presents itself in succession, or at most only as much as a convex mirror has, whose rays converge at an imaginary point behind its surface. But it is *the will* alone that is permanent and unchangeable in consciousness. It is the will that holds all ideas and representations together as means to its ends, tinges them with the colour of its character, its mood, and its interest, commands the attention, and holds the thread of motives in its hand. The influence of these motives ultimately puts into action memory and the association of ideas. Fundamentally it is the will that is spoken of whenever “I” occurs in a judgement. Therefore, the will is the true and ultimate point of unity of consciousness, and the bond of all its functions and acts. It does not, however, itself belong to the intellect, but is only its root, origin, and controller.—from_The World as Will and Representation_. Translated from the German by E. F. J. Payne in two volumes: volume II, pp. 139-140

~ Arthur Schopenhauer