Arthur Schopenhauer said this quote

“ 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 ”