On The Holy Trinity by St. Augustine
Chapter 9.--Species is Produced by Species in Succession.
16. In this arrangement, then, while we begin from the bodily species and arrive finally at the species which comes to be in the intuition (contuitu) of the concipient, we find four species born, as it were, step by step one from the other, the second from the first, the third from the second, the fourth from the third: since from the species of the body itself, there arises that which comes to be in the sense of the percipient; and from this, that which comes to be in the memory; and from this, that which comes to be in the mind's eye of the concipient. And the will, therefore, thrice combines as it were parent with offspring: first the species of the body with that to which it gives birth in the sense of the body; and that again with that which from it comes to be in the memory; and this also, thirdly, with that which is born from it in the intuition of the concipient's mind. But the intermediate combination which is the second, although it is nearer to the first, is yet not so like the first as the third is. For there are two kinds of vision, the one of [sensuous] perception (sentientis), the other of conception (cogitantis). But in order that the vision of conception may come to be, there is wrought for the purpose, in the memory, from the vision of [sensuous] perception something like it, to which the eye of the mind may turn itself in conceiving, as the glance (acies) of the eyes turns itself in [sensuously] perceiving to the bodily object. I have, therefore, chosen to put forward two trinities in this kind: one when the vision of [sensuous] perception is formed from the bodily object, the other when the vision of conception is formed from the memory. But I have refrained from commending an intermediate one; because we do not commonly call it vision, when the form which comes to be in the sense of him who perceives, is entrusted to the memory. Yet in all cases the will does not appear unless as the combiner as it were of parent and offspring; and so, proceed from whence it may, it can be called neither parent nor offspring.