Friends hold a mirror up to each other; through that mirror they can see each other in ways that would not otherwise be accessible to them, and it is this mirroring that helps them improve themselves as persons.
There are three qualifications required in those who have to fill the highest offices, - (1) first of all, loyalty to the established constitution; (2) the greatest administrative capacity; (3) virtue and justice of the kind proper to each form of government.
Since we think we understand when we know the explanation, and there are four types of explanation (one, what it is to be a thing; one, that if certain things hold it is necessary that this does; another, what initiated the change; and fourth, the aim), all these are proved through the middle term.