The father of philosophy, Socrates of Athens (468-399 B.C.), sought to counter these lawless views by finding a basis for the virtues in the real needs of a man's best self. Philosophy before him had been busy with the study of the external world and the constitution of matter. Man had always wanted to know what the world is made of and how natural phenomena occur, but before Greek philosophy began he had been satisfied with a personal explanationit was Zeus who sent the lightning. Thales, in the early sixth century B.C., brushed aside such explanations and said that the original substance was moisture. Other philosophers developed the idea of the four elements, earth, air, fire, and water. Pythagoras, a great geometrician and scientist, said that " things were numbers," that is, that the real essence of the world is to be found in proportion and mathematical relations. Democritus said that the world consisted of an infinite number of atoms moving about in infinite space. Before Socrates man had given examples instead of definitions and had said that courage consisted of fighting bravely in battle. Socrates wanted to find a definition that would fit all the aspects of goodness. His own answer was that virtue was knowledge, that no one errs knowingly, but only because he thinks that he is benefiting himself. But this answer, which overlooked the element of will in deciding on an action, failed to solve the problem involved in the sentence " I see and approve the better course, but I follow the worse." The great achievement of Socrates was to concentrate inquiry, not on the world without, but on the soul within ; to ask " What is the good, and what are the relations of justice and courage and temperance and prudence to each other ? " His dialectic, with its constant cross-examination, undermined the old beliefs without making shallow minds realise that devotion to truth should be the driving force of life. Some young men who had taken part in discussion with him attempted in 404 B.C. to overthrow the democracy. The attempt failed, but Socrates was accused of corrupting the youths and was condemned. Plato's description of his last hours is hardly inferior in pathos and majesty to the New Testament story of the death of Christ. The life of Socrates shows that the perfect identity between citizen and city which had made Athens so splendid was breaking down. Men were beginning to think that the individual could develop a life of his own apart from the state.