3 But stay: let us see what is that indefinable object which is suggested to the mind. This world with which our senses acquaint us is surely the image of some world which the understanding apprehends. Now it is a strange phenomenon which we observe in the images which mirrors reflect to us—that however great the mirrors be, they do not make the images larger than the objects placed before them, be they ever so small; but in small mirrors, such as the pupil of the eye, although a large surface be placed over against them, a very small image is formed, proportioned to the size of the mirror. Therefore if the mirrors be reduced in size, the images reflected in them are also reduced; but it is not possible for the images to be enlarged by enlarging the mirrors. Surely there is in this something which might reward further investigation; but meanwhile, I must sleep. Moreover, if I seem to Nebridius to be happy, it is not because I seek, but because perchance I have found something. What, then, is that something? Is it that chain of reasoning which I am wont so to caress as if it were my sole treasure, and in which perhaps I take too much delight?
Source: Letters (New Advent)