We must lop, dig, bind, and perform the other operations. The pruning-knife, I should think, and the pick-axe, and the other agricultural implements, are necessary for the culture of the vine, so that it may produce eatable fruit. And as in husbandry, so also in medicine: he has learned to purpose, who has practised the various lessons, so as to be able to cultivate and to heal. So also here, I call him truly learned who brings everything to bear on the truth; so that, from geometry, and music, and grammar, and philosophy itself, culling what is useful, he guards the faith against assault. Now, as was said, the athlete is despised who is not furnished for the contest. For instance, too, we praise the experienced helmsman who “has seen the cities of many men,” and the physician who has had large experience; thus also some describe the empiric.[882] And he who brings everything to bear on a right life, procuring examples from the Greeks and barbarians, this man is an experienced searcher after truth, and in reality a man of much counsel, like the touchstone (that is, the Lydian), which is believed to possess the power of distinguishing the spurious from the genuine gold. And our much-knowing gnostic can distinguish sophistry from philosophy, the art of decoration from gymnastics, cookery from physic, and rhetoric from dialectics, and the other sects which are according to the barbarian philosophy, from the truth itself. And how necessary is it for him who desires to be partaker of the power of God, to treat of intellectual subjects by philosophising! And how serviceable is it to distinguish expressions which are ambiguous, and which in the Testaments are used synonymously! For the Lord, at the time of His temptation, skilfully matched the devil by an ambiguous expression. And I do not yet, in this connection, see how in the world the inventor of philosophy and dialectics, as some suppose, is seduced through being deceived by the form of speech which consists in ambiguity. And if the prophets and apostles knew not the arts by which the exercises of philosophy are exhibited, yet the mind of the prophetic and instructive spirit, uttered secretly, because all have not an intelligent ear, demands skilful modes of teaching in order to clear exposition. For the prophets and disciples of the Spirit knew infallibly their mind. For they knew it by faith, in a way which others could not easily, as the Spirit has said. But it is not possible for those who have not learned to receive it thus. “Write,” it is said, “the commandments doubly, in counsel and knowledge, that thou mayest answer the words of truth to them who send unto thee.”[883] What, then, is the knowledge of answering? or what that of asking? It is dialectics. What then? Is not speaking our business, and does not action proceed from the Word? For if we act not for the Word, we shall act against reason. But a rational work is accomplished through God.