For they used to suppose that they trained people by imparting to them not the art but its products, as though anyone professing that he would impart a form of knowledge to obviate any pain in the feet, were then not to teach a man the art of shoe making or the sources whence he can acquire anything of the kind, but were to present him with several kinds of shoes of all sorts for he has helped him to meet his need, but has not imparted an art to him.