Right here, however, a just criticism may be made of the Socratic philosophy. It is true that without self-knowledge, without the fulfilling of the Delphian requirement, “Know thyself,” one cannot be truly moral. But neither Socrates nor the Greek philosophers in general recognized that this self-knowledge comes through right living rather than through right thinking. As Goethe discerningly observes, man comes to know himself not through reflection but through conduct: “Do your duty and thou wilt know what thou art.”[500] And for the common moral life of the world there is a profound teaching in this Socratic doctrine which makes knowledge the spring of virtue.[501] There is in knowledge, in insight, in the clear recognition of the relation of man’s highest good to virtue, an impelling force and authority. As the world advances in true knowledge, it will advance in true morality. The Renaissance is ever the precursor of the Reformation. It is this fact which should make optimists of us all, for the unceasing advance of the world in knowledge is well assured. In the ethical system of Socrates we have a good illustration of the truth that great men are the product of their age. With all his originality and profound spiritual insight, Socrates could not and did not rise much above the plane of the common moral consciousness of his contemporaries. He stood on essentially Greek ground. His morality was the morality of his time and place. In his practical code of morals he made the Greek virtue of self-control or moderation a cardinal virtue; he laid the Greek emphasis upon the civic virtues, dying rather than disobey or evade the decree of his city; he entertained the common Greek ideas respecting the family and the domestic virtues; he saw nothing to disapprove in the life of the hetæra; he viewed the beautiful from a standpoint wholly Greek, almost identifying beauty with goodness; he was thoroughly Greek in the aristocratic tendency of his ethical teachings, making the practice of true virtue the prerogative of the cultured class alone; he had the ordinary Greek conscience in regard to slavery; and he never detached himself from that narrow Greek prejudice which saw in the Hellenes the elect race. He never proclaimed, as did many a later Greek and Roman moralist, the essential unity of the human race. [Sidenote: Plato and his ethical system] Socrates made virtue and man’s moral nature the subject of philosophic reflection. His pupil, Plato, systematized his master’s teachings, and, reducing these and the common ethical notions of his time to scientific form laid the basis of the science of ethics.