For both excessive and insufficient exercise destroy one's strength, and both eating and drinking too much or too little destroy health, whereas the right quantity produces, increases and preserves it. So it is the same with temperance, courage and the other virtues. This much then, is clear: in all our conduct it is the mean that is to be commended.
That in the soul which is called mind (by mind I mean that whereby the soul thinks and judges) is, before it thinks, not actually any real thing. For this reason it cannot reasonably be regarded as blended with the body
...in this way the structure of the universe- I mean, of the heavens and the earth and the whole world- was arranged by one harmony through the blending of the most opposite principles.
The citizens begin by giving up some part of the constitution, and so with greater ease the government change something else which is a little more important, until they have undermined the whole fabric of the state.
If thinking is like perceiving, it must be either a process in which the soul is acted upon by what is capable of being thought, or a process different from but analogous to that. The thinking part of the soul must therefore be, while impassable, capable of receiving the form of an object; that is, must be potentially identical in character with its object without being the object. Mind must be related to what is thinkable, as sense is to what is sensible.
Even if we could suppose the citizen body to be virtuous, without each of them being so, yet the latter would be better, for in the virtue of each the virtue of all is involved.
The good of man is the active exercise of his soul's faculties. This exercise must occupy a complete lifetime. One swallow does make a spring, nor does one fine day. Excellence is a habit, not an event.