Aldous Huxley (1894-1963), "Books for the Journey," Along the Road: Notes and Essays of a Tourist (London: Chatto & Windus, 1925; rpt. 1948), pp. 63-71 (at 70-71):
A stray volume of the Encyclopaedia is like the mind of a learned madman—stored with correct ideas, between which, however, there is no other connection than the fact that there is a B in both; from orach, or mountain spinach, one passes directly to oracles. That one does not oneself go mad, or become, in the process of reading the Encyclopaedia, a mine of useless and unrelated knowledge is due to the fact that one forgets. The mind has a vast capacity for oblivion. Providentially; otherwise, in the chaos of futile memories, it would be impossible to remember anything useful or coherent. In practice, we work with generalizations, abstracted out of the turmoil of realities. If we remembered everything perfectly, we should never be able to generalize at all, for there would appear before our minds nothing but individual images, precise and different. Without ignorance we could not generalize. Let us thank Heaven for our powers of forgetting. With regard to the Encyclopaedia they are enormous. The mind only remembers that of which it has some need. Five minutes after reading about mountain spinach, the ordinary man, who is neither a botanist nor a cook, has forgotten all about it. Read for amusement, the Encyclopaedia serves only to distract for the moment; it does not instruct, it deposits nothing on the surface of the mind that will remain. It is a mere time-killer and momentary tickler of the mind.