The structural unity of the parts is such that, if any one of them is displaced or removed, the whole will be disjointed and disturbed. For a thing whose presence or absence makes no visible difference is not an organic part of the whole.
For just as for a flute-player, a sculptor, or an artist, and, in general, for all things that have a function or activity, the good and the well is thought to reside in the function, so would it seem to be for man, if he has a function.
If, then, there is some end of the things we do, which we desire for its own sake (everything else being desired for the sake of this), and if we do not choose everything for the sake of something else (for at that rate the process would go on to infinity, so that our desire would be empty and vain), clearly this must be the good and the chief good.
It is just that we should be grateful, not only to those with whose views we may agree, but also to those who have expressed more superficial views; for these also contributed something, by developing before us the powers of thought.
Tragedy is an imitation not only of a complete action, but of events inspiring fear and pity. Such an effect is best produced when the events come on us by surprise; and the effect is heightened when, at the same time, they follow as cause and effect. The tragic wonder will then be great than if they happened of themselves or by accident; for even coincidences are most striking when they have an air of design.