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.
Between knowledge of what really exists and ignorance of what does not exist lies the domain of opinion. It is more obscure than knowledge, but clearer than ignorance.
Herein is the evil of ignorance, that he who is neither good nor wise is nevertheless satisfied with himself: he had no desire for that of which he feels no want.
If anyone comes to the gates of poetry and expects to become an adequate poet by acquiring expert knowledge of the subject without the Muses' madness, he will fail, and his self-controlled verses will be eclipsed by the poetry of men who have been driven out of their minds.
For a man to conquer himself is the first and noblest of all victories... The first and greatest victory is to conquer yourself; to be conquered by yourself is of all things most shameful and vile.
Too much attention to health is a hindrance to learning, to invention, and to studies of any kind, for we are always feeling suspicious shootings and swimmings in our heads, and we are prone to blame studies from them.