18. Wherefore we find that to learn these things, whose images we drink not in by our senses, but perceive within as they axe by themselves, without images, is nothing else but by meditation as it were to concentrate, and by observing to take care that those notions which the memory did before contain scattered and confused, be laid up at hand, as it were, in that same memory, where before they lay concealed, scattered and neglected, and so the more easily present themselves to the mind well accustomed to observe them. And how many things of this sort does my memory retain which have been found out already, and, as I said, are, as it were, laid up ready to hand, which we are said to have learned and to have known; which, should we for small. intervals of time cease to recall, they are again so submerged and slide back, as it were, into the more remote chambers, that they must be evolved thence again as if new (for other sphere they have none), and must be marshalled [cogenda] again that they may become known; that is to say, they must be collected [calligenda], as it were, from their dispersion; whence we have the word cagitare. For cogo lit collect] and cogira [I re-collect] have the same relation to each other as ago and agito, lucia and factira. But the mind has appropriated to itself this word [cogitation], so that not that which is collected anywhere, but what is collected,x that is marshalled. in the mind, is properly said to be "cogitated."'