But is Socrates serious in maintaining (1) that virtue cannot be taught; (2) that the virtues are one; (3) that virtue is the knowledge of pleasures and pains present and future? These propositions to us have an appearance of paradox--they are really moments or aspects of the truth by the help of which we pass from the old conventional morality to a higher conception of virtue and knowledge. That virtue cannot be taught is a paradox of the same sort as the profession of Socrates that he knew nothing. Plato means to say that virtue is not brought to a man, but must be drawn out of him; and cannot be taught by rhetorical discourses or citations from the poets. The second question, whether the virtues are one or many, though at first sight distinct, is really a part of the same subject; for if the virtues are to be taught, they must be reducible to a common principle; and this common principle is found to be knowledge. Here, as Aristotle remarks, Socrates and Plato outstep the truth--they make a part of virtue into the whole. Further, the nature of this knowledge, which is assumed to be a knowledge of pleasures and pains, appears to us too superficial and at variance with the spirit of Plato himself. Yet, in this, Plato is only following the historical Socrates as he is depicted to us in Xenophon's Memorabilia. Like Socrates, he finds on the surface of human life one common bond by which the virtues are united,--their tendency to produce happiness,--though such a principle is afterwards repudiated by him.