The science [geometry] is pursued for the sake of the knowledge of what eternally exists, and not of what comes for a moment into existence, and then perishes.
The beginning is the most important part of any work, especially in the case of a young and tender thing; for that is the time at which the character is being formed and the desired impression is more readily taken.
I would have you imagine, then, that there exists in the mind of man a block of wax... and that we remember and know what is imprinted as long as the image lasts; but when the image is effaced, or cannot be taken, then we forget or do not know.
Wherefore also these Kinds [elements] occupied different places even before the universe was organised and generated out of them. Before that time, in truth, all these were in a state devoid of reason or measure, but when the work of setting in order this Universe was being undertaken, fire and water and earth and air, although possessing some traces of their known nature, were yet disposed as everything is likely to be in the absence of God; and inasmuch as this was then their natural condition, God began by first marking them out into shapes by means of forms and numbers.
Everything desires not like but unlike: for example, the dry desires the moist, the cold the hot, the bitter the sweet, the sharp the blunt, the void the full, the full the void, and so of all other things; for the opposite is the food of the opposite, whereas like receives like receives nothing from like.
Any one who has common sense will remember that the bewilderments of the eyes are of two kinds, and arise from two causes, either from coming out of the light or from going into the light, which is true of the mind's eye, quite as much as of the bodily eye; and he who remembers this when he sees any one whose vision is perplexed and weak, will not be too ready to laugh; he will first ask whether that soul of man has come out of the brighter light, and is unable to see because unaccustomed to the dark, or having turned from darkness to the day is dazzled by excess of light.
Because, unlike courage and wisdom, which made our state brave and wise by being present in a particular part of it, discipline operates by being diffused throughout the whole of it. It produces a concord between its strongest and weakest and middle elements, whether you define them by the standard of good sense, or of strength, or of numbers or money or the like. And so we are quite justified in regarding discipline as this sort of natural harmony and agreement between higher and lower about which of them is to rule in state and individual.
Interference by the three classes with each other s jobs, and interchange of jobs between them, therefore, does the greatest harm to our state, and we are entirely justified in calling it the worst of evils.
Do you, like a skilful weigher, put into the balance the pleasures and the pains, near and distant, and weigh them, and then say which outweighs the other? If you weigh pleasures against pleasures, you of course take the more and greater; or if you weigh pains against pains, then you choose that course of action in which the painful is exceeded by the pleasant, whether the distant by the near or the near by the distant; and you avoid that course of action in which the pleasant is exceeded by the painful.