This view of the problem of philosophy is more precisely defined by the Stoic doctrine of virtue. Philosophy should lead to right action and to virtue. But right action is, according to the Stoics, only rational action, and rational action is action which is in harmony with human and inanimate nature. Virtue consists therefore in bringing man’s actions into harmony with the laws of the universe, and with the general order of the world. This is only possible when man knows that order and those laws; and thus the Stoics are brought back to the principles of Socrates, that virtue may be learnt; that knowledge is indispensable for virtue, or rather that virtue is identical with right knowledge. They define virtue in so many words as knowledge, vice as ignorance. If sometimes they seem to identify virtue with strength of will, it is only because they consider strength of will to be inseparable from knowledge, so that the one cannot be conceived without the other. Hence the practical study of philosophy conducts with them to the intellectual; philosophy is not only virtue, but without philosophy no virtue is possible. [75] Granting that the attainment of virtue, and the happiness of a moral life, are the chief ends which the Stoics propose to themselves, still the possession of a comprehensive scientific knowledge is indispensable, as the only means thereto. [(3) Position towards logic and natural science.] [(a) Aristo’s views.] These remarks prove the need for the Stoics of that kind of scientific knowledge which has to do with life, the morals and the actions of mankind, in short, of Ethics. Whether further scientific knowledge is necessary, was a question on which the earliest adherents of the Stoic teaching expressed different opinions. Zeno’s pupil, Aristo of Chios, held that the sole business of man is to pursue virtue, [76] and that the sole use of language is to purify the soul. [77] This purifying process, however, is neither to be found in logical subtleties nor in natural science. Logic, as doing more harm than good, he compared to a spider’s web, which is as useless as it is curious; [78] or else to the mud on a road. [79] Those who studied it he likened to people eating lobsters, who take a great deal of trouble for the sake of a little bit of meat enveloped in much shell. [80] Convinced, too, that the wise man is free from every deceptive infatuation, [81] and that doubt, for the purpose of refuting which logic has been invented, can be more easily overcome by a healthy tone of mind [82] than by argument, he felt no particular necessity for logic. Nay, more, he considered that excessive subtlety transforms the healthy action of philosophy into an unhealthy one. [83] Just as little was Aristo disposed to favour the so-called encyclical knowledge: those who devote themselves to this knowledge instead of to philosophy he compared to the suitors of Penelope, who won the maids but not the mistress. [84] Natural science would probably