But they thought that all the senses were dull and slow, and that they did not by any means perceive those things which appeared subjected to the senses; which were either so small as to be unable to come under the notice of sense, or so moveable and rapid that none of them was ever one consistent thing, nor even the same thing, because everything was in a continual state of transition and disappearance. And therefore they called all this division of things one resting wholly on opinion. But they thought that science had no existence anywhere except in the notions and reasonings of the mind; on which account they approved of the definitions of things, and employed them on everything which was brought under discussion. The explanation of words also was approved of—that is to say, the explanation of the cause why everything was named as it was; and that they called etymology. Afterwards they used arguments, and, as it were, marks of things, for the proof and conclusion of what they wished to have explained; in which the whole system of dialectics—that is to say, of an oration brought to its conclusion by ratiocination, was handed down. And to this there was added, as a kind of second part, the oratorical power of speaking, which consists in developing a continued discourse, composed in a manner adapted to produce conviction. IX. This was the first philosophy handed down to them by Plato. And if you like I will explain to you those discussions which have originated in it. Indeed, said I, we shall be glad if you will; and I can answer for Atticus as well as for myself. You are quite right, said he; for the doctrine both of the Peripatetics and of the old Academy is most admirably explained.