Then I will tell you, said Socrates. When I was young, Cebes, I had a prodigious desire to know that department of philosophy which is called the investigation of nature; to know the causes of things, and why a thing is and is created or destroyed appeared to me to be a lofty profession; and I was always agitating myself with the consideration of questions such as these:--Is the growth of animals the result of some decay which the hot and cold principle contracts, as some have said? Is the blood the element with which we think, or the air, or the fire? or perhaps nothing of the kind--but the brain may be the originating power of the perceptions of hearing and sight and smell, and memory and opinion may come from them, and science may be based on memory and opinion when they have attained fixity. And then I went on to examine the corruption of them, and then to the things of heaven and earth, and at last I concluded myself to be utterly and absolutely incapable of these enquiries, as I will satisfactorily prove to you. For I was fascinated by them to such a degree that my eyes grew blind to things which I had seemed to myself, and also to others, to know quite well; I forgot what I had before thought self-evident truths; e.g. such a fact as that the growth of man is the result of eating and drinking; for when by the digestion of food flesh is added to flesh and bone to bone, and whenever there is an aggregation of congenial elements, the lesser bulk becomes larger and the small man great. Was not that a reasonable notion? Yes, said Cebes, I think so. Well; but let me tell you something more. There was a time when I thought that I understood the meaning of greater and less pretty well; and when I saw a great man standing by a little one, I fancied that one was taller than the other by a head; or one horse would appear to be greater than another horse: and still more clearly did I seem to perceive that ten is two more than eight, and that two cubits are more than one, because two is the double of one. And what is now your notion of such matters? said Cebes.