On The Holy Trinity by St. Augustine
Chapter 10.--The Imagination Also Adds Even to Things We Have Not Seen, Those Things Which We Have Seen Elsewhere.
17. But if we do not remember except what we have [sensuously] perceived, nor conceive except what we remember; why do we often conceive things that are false, when certainly we do not remember falsely those things which we have perceived, unless it be because that will (which I have already taken pains to show as much as I can to be the uniter and the separater of things of this kind) leads the vision of the conceiver that is to be formed, after its own will and pleasure, through the hidden stores of the memory; and, in order to conceive [imagine] those things which we do not remember, impels it to take one thing from hence, and another from thence, from those which we do remember; and these things combining into one vision make something which is called false, because it either does not exist externally in the nature of corporeal things, or does not seem copied from the memory, in that we do not remember that we ever saw such a thing. For who ever saw a black swan? And therefore no one remembers a black swan; yet who is there that cannot conceive it? For it is easy to apply to that shape which we have come to know by seeing it, a black color, which we have not the less seen in other bodies; and because we have seen both, we remember both. Neither do I remember a bird with four feet, because I never saw one; but I contemplate such a phantasy very easily, by adding to some winged shape such as I have seen, two other feet, such as I have likewise seen. And therefore, in conceiving conjointly, what we remember to have seen singly, we seem not to conceive that which we remember; while we really do this under the law of the memory, whence we take everything which we join together after our own pleasure in manifold and diverse ways. For we do not conceive even the very magnitudes of bodies, which magnitudes we never saw, without help of the memory; for the measure of space to which our gaze commonly reaches through the magnitude of the world, is the measure also to which we enlarge the bulk of bodies, whatever they may be, when we conceive them as great as we can. And reason, indeed, proceeds still beyond, but phantasy does not follow her; as when reason announces the infinity of number also, which no vision of him who conceives according to corporeal things can apprehend. The same reason also teaches that the most minute atoms are infinitely divisible; yet when we have come to those slight and minute particles which we remember to have seen, then we can no longer behold phantasms more slender and more minute, although reason does not cease to continue to divide them. So we conceive no corporeal things, except either those we remember, or from those things which we remember.