This experiment succeeds as hoped and promises to metaphysics, in its first part, which deals with those *a priori* concepts to which the corresponding objects may be given in experience, the secure course of a science. For by thus changing our point of view, the possibility of *a priori* knowledge can well be explained, and, what is still more, the laws which *a priori* lie at the foundation of nature, as the sum total of the objects of experience, may be supplied with satisfactory proofs, neither of which was possible within the procedure hitherto adopted. But there arises from this deduction of our faculty of knowing *a priori*, as given in the first part of metaphysics, a somewhat startling result, apparently most detrimental to that purpose of metaphysics which has to be treated in its second part, namely the impossibly of using this faculty to transcend the limits of possible experience, which is precisely the most essential concern of the science of metaphysics. But here we have exactly the experiment which, by disproving the opposite, establishes the truth of the first estimate of our *a priori* rational knowledge, namely, that it is directed only at appearances and must leave the thing in itself as real for itself but unknown to us. For that which necessarily impels us to to go beyond the limits of experience and of all appearances is the *unconditioned*, which reason rightfully and necessarily demands, aside from everything conditioned, in all things in themselves, so that the series of conditions be completed. If, then, we find that, under the supposition that our empirical knowledge conforms to objects as things in themselves, the unconditioned *cannot be thought without contradiction*, while under the supposition that our representation of things as they are given to us does not conform to them as things in themselves, but, on the contrary, that these objects as appearance conform to our mode of representation, then *the contradiction vanishes*; and if we find, therefore, that the unconditioned cannot be encountered in things insofar as we are acquainted with them (insofar as they are given to us), but only in things insofar as we are not acquainted with them, that is, insofar as they are things in themselves; then it becomes apparent that what we at first assumed only for the sake of experiment is well founded. However, with speculative reason unable to make progress in the field of the supersensible, it is still open to us to investigate whether in reason's practical knowledge data may not be found which would enable us to determine that transcendent rational concept of the unconditioned, so as to allow us, in accordance with the wish of metaphysics, to get beyond the limits of all possible experience with our *a priori* knowledge, which is possible in practical matters only. Within such a procedure, speculative reason has always at least created a space for such an expansion, even if it has to leave it empty; none the less we are at liberty, indeed we are summoned, to fill it, if we are able to do so, with practical *data* of reason.―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. 19-21

~ Immanuel Kant

From *the form of time and of the single dimension* of the series of representations, on account of which the intellect, in order to take up one thing, must drop everything else, there follows not only the intellect’s distraction, but also its *forgetfulness*. Most of what it has dropped it never takes up again, especially as the taking up again is bound to the principle of sufficient reason, and thus requires an occasion which the association of ideas and motivation have first to provide. Yet this occasion may be the remoter and the smaller, the more our susceptibility to it is enhanced by interest in the subject. But, as I have already shown in the essay *On the Principle of Sufficient Reason*, memory is not a receptacle, but a mere faculty, acquired by practice, of bringing forth any representations at random, so that these have always to be kept in practice by repetition, otherwise they are gradually lost. Accordingly, the knowledge even of the scholarly head exists only *virtualiter* as an acquired practice in producing certain representations. *Actualiter*, on the other hand, it is restricted to one particular representation, and for the moment is conscious of this one alone. Hence there results a strange contrast between what a man knows *potentia* and what he knows *actu*, in other words, between his knowledge and his thinking at any moment. The former is an immense and always somewhat chaotic mass, the latter a single, distinct thought. The relation is like that between the innumerable stars of the heavens and the telescope’s narrow field of vision; it stands out remarkably when, on some occasion, a man wishes to bring to distinct recollection some isolated fact from his knowledge, and time and trouble are required to look for it and pick it out of that chaos. Rapidity in doing this is a special gift, but depends very much on the day and the hour; therefore sometimes memory refuses its service, even in things which, at another time, it has ready at hand. This consideration requires us in our studies to strive after the attainment of correct insight rather than an increase of learning, and to take to heart the fact that the *quality* of knowledge is more important than its quantity. Quantity gives books only thickness; quality imparts thoroughness as well as style; for it is an *intensive* dimension, whereas the other is merely extensive. It consists in the distinctness and completeness of the concepts, together with the purity and accuracy of the knowledge of perception that forms their foundation. Therefore the whole of knowledge in all its parts is permeated by it, and is valuable or troubling accordingly. With a small quantity but good quality of knowledge we achieve more than with a very great quantity but bad quality.—from_The World as Will and Representation_. Translated from the German by E. F. J. Payne in two volumes: volume II, pp. 139-141

~ Arthur Schopenhauer