We have no evidence as yet about mind or the power to think; it seems to be a widely different kind of soul, differing as what is eternal from what is perishable; it alone is capable of existence in isolation from all other psychic powers.
If there is some end of the things we do, which we desire for its own sake, clearly this must be the good. Will not knowledge of it, then, have a great influence on life? Shall we not, like archers who have a mark to aim at, be more likely to hit upon what we should? If so, we must try, in outline at least, to determine what it is.
The so-called Pythagoreans, who were the first to take up mathematics, not only advanced this subject, but saturated with it, they fancied that the principles of mathematics were the principles of all things.
Of the tyrant, spies and informers are the principal instruments. War is his favorite occupation, for the sake of engrossing the attention of the people, and making himself necessary to them as their leader.
For knowing is spoken of in three ways: it may be either universal knowledge or knowledge proper to the matter in hand or actualising such knowledge; consequently three kinds of error also are possible.
Property should be in a certain sense common, but, as a general rule, private; for, when every one has a distinct interest, men will not complain of one another, and they will make more progress, because every one will be attending to his own business.
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.
Anaximenes and Anaxagoras and Democritus say that its [the earth's] flatness is responsible for it staying still: for it does not cut the air beneath but covers it like a lid, which flat bodies evidently do: for they are hard to move even for the winds, on account of their resistance.
But since there is but one aim for the entire state, it follows that education must be one and the same for all, and that the responsibility for it must be a public one, not the private affair which it now is, each man looking after his own children and teaching them privately whatever private curriculum he thinks they ought to study.
And so long as they were at war, their power was preserved, but when they had attained empire they fell, for of the arts of peace they knew nothing, and had never engaged in any employment higher than war.
Since the whole city has one end, it is manifest that education should be one and the same for all, and that it should be public, and not private - not as at present, when every one looks after his own children separately, and gives them separate instruction of the sort which he thinks best; the training in things which are of common interest should be the same for all. Neither must we suppose that any one of the citizens belongs to himself, for they all belong to the state, and are each of them a part of the state, and the care of each part is inseparable from the care of the whole.