Averroes' Paraphrase of Plato's Republic

For as that final part contains, and teaches what is healthy for educating bodies, what preserves health in them, and if ever they have retreated from health, by what reason illnesses are removed: so also the matter stands here.
3rd that habit/virtue be described

The third remains, that we describe what a habit is, or virtue: which, if it be joined to any other virtue, the act of that virtue is rendered more exact; furthermore, which habit serves another, just as a physician says that this affection, joined to that one, induces and preserves health in bodies. All these things will be understood quite easily once the end and purpose of all these virtues are understood, insofar as they are parts of the Republic. It is just like the protection of the health of the limbs and the restoration of the same, which is indeed known most frequently when the reason and order of all the members among themselves are known. Having exposed these things in this way, finally, the path must be explained by which we might find the virtues in the minds of citizens, and in what manner. And if this should not escape you, for virtues to exist in the Republic in reality, and similarly in the people, it is not enough to explain it in speech, until a certain faculty of conjecture is applied to this, as is done in the art of medicine. And from this it can be gathered that the rudders of the Republic are owed to the elders; since they, besides the fact that they have attained speculative sciences, also possess experience acquired over a long time: not otherwise than a physician
that government is for the elder