Metaphysics is a dark ocean without shores or lighthouse, strewn with many a philosophic wreck.

We have seen, therefore, that I am not allowed even to *assume*, for the sake of the necessary practical use of my reason *God, freedom, immortality*, unless at the same time *I deprive* speculative reason of its pretensions to transcendent insights. Reason, namely, in order to arrive at these, must employ principles which extend only to objects of possible experience, and which, if in spite of this they are applied also to what cannot be an object of experience, actually always change this into an appearance, thus rendering all practical *expansion* of pure reason impossible. Hence I had to suspend *knowledge* in order to make room for *belief*. For the dogmatism of metaphysics without a preceding critique of pure reason, is the source of all that disbelief which opposes morality and which is always very dogmatic.

Our critique is not opposed to the *dogmatic procedure* of reason in its pure knowledge as science (for science must always be dogmatic, that is, derive its proof from secure *a priori* principles), but only to *dogmatism*, that is, to the presumption that it is possible to make any progress with pure (philosophical) knowledge from concepts according to principles, such as reason has long been in the habit of using, without first inquiring in what way, and by what right, it has come to posses them. Dogmatism is therefore the dogmatic procedure of pure reason, *without a preceding critique of its own powers*; and our opposition to this is not intended to defend that loquacious shallowness which arrogates to itself the name of popularity, much less that skepticism which makes short work of the whole of metaphysics. On the contrary, our critique is meant to form a necessary preparation in support of metaphysics as a thorough science, which must necessarily be carried out dogmatically and strictly systematically, so as to satisfy all the demands, no so much of the public at large, as of the Schools. This is an indispensable demand for it has undertaken to carry out its work entirely *a priori*, and thus to carry it out to the complete satisfaction of speculative reason. In the execution of this plan, as traced out by the critique, that is, in a future system of metaphysics, we shall have to follow the strict method of the celebrated Wolff, the greatest of all dogmatic philosophers. He was the first to give an example (and by his example initiated, in Germany, that spirit of thoroughness which is not yet extinct) of how the secure course of a science could be attained only through the lawful establishment of principles, the clear determination of concepts, the attempt at strictness of proof and avoidance of taking bold leaps in our inferences. He was therefore most eminently qualified to give metaphysics the dignity of a science, if it had only occurred to him to prepare his field in advance by criticism of the organ, that is, of pure reason itself―an omission due not so much to himself as to the dogmatic mentality of his age, about which the philosophers of his own, as well as of all previous times, have no right to reproach one another. Those who reject both the method of Wolff and the procedure of the critique of pure reason can have no other aim but to shake off the fetters of *science* altogether, and thus to change work into play, certainty into opinion and philosophy into philodoxy."

―from_Critique of Pure Reason_. Preface to the Second Edition. Translated, edited, and with an Introduction by Marcus Weigelt, based on the translation by Max Müller, pp. 28-29

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

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

Thoughts without content are empty, intuitions without concepts are blind.