The argument of the Sophists that what is best for the individual is best for society aroused the antagonism of Socrates (469–399 B. C.), whose ideas are reported by Plato and Xenophon. Socrates, the son of an Athenian sculptor, asserted that the qualities of justice, wisdom, temperance, and courage, which make a person a good member of society and which increase social welfare, are the same qualities which make a person a good individual and secure his individual advancement. Socrates spent many years at the market places, on the streets where people congregate and at the public resorts in studying the actions of individuals and in engaging them in conversation concerning their moral life. As a result Socrates evolved a significant social philosophy. The heart of this philosophy is found in the statements that virtue is knowledge, not in the sense of mere memorized facts but of a thorough understanding. If a person understands completely the good and evil phases of a proposed act, he will choose the right. For example, when one is completely convinced of the harmful effects of poor teeth, he will employ the regular services of a dentist to keep his teeth in good condition. When he perceives the evil effects of dishonesty, he will establish honest habits. The conclusion might be drawn that social virtue rests upon societary knowledge. Socrates was convinced that something was fundamentally wrong with Athenian society. Everywhere he saw that ignorance led to vice. Only in the mechanical and professional activities did he discover correct action, but this was preceded by correct knowledge.[V-9] A good carpenter is an individual who thoroughly understands carpentry; a good man is an individual who truly knows the value of good actions. Similarly, it might be said that a good urban resident is an individual who deeply appreciates what it means to have a city of mutually developing people. Socrates wished to make all men intelligent. His teachings raised the deep-seated social question: How can social organization be made highly advantageous to the individual, and the individual made so aware of these advantages that he will always act socially?[V-10] Inasmuch as Socrates left no writings, it is impossible to explain with certainty his teachings. Fortunately, he left a permanent impress of his personality on the lives of his associates, and particularly, upon his able and brilliant pupil, Plato.