According to Aristotle, the young have strong but changeable passions. They are quick tempered and lacking in self-control, and this makes them all the more likely to yield to their passions. They are eager for superiority and easily feel slighted. They love honour and victory more than money, and would rather do noble deeds than useful ones. As the greater part of their life lies before them, they live more in expectation than in memory; and as they are lacking in experience, they have exalted notions and tend to see the good rather than the bad. Although they are confident and courageous, they are still accepting of the rules of their society; and although they like spending their days with others, they have not yet learned to value their friends for their usefulness. They are quick to pity because they think that everyone is honest. If they wrong others, this is more to insult than to do real harm. As they are fond of fun, they are witty – wit being nothing other than well-bred insolence. They think they know everything and so they overdo everything. This is the source of all their mistakes.
In contrast to the young, the elderly live by memory rather than by hope. As they have a lot of experience, they are sure about nothing and under-do everything. They are small-minded because they have been humbled by life. As a result, they are driven too much by the useful and not enough by the noble. They are cynical and distrustful and neither love warmly nor hate bitterly. They are not shy but rather shameless, and feel only contempt for people’s opinion of them. As that which is desired most strongly is that which is needed most urgently, they love life, and all the more when their last day has arrived.
The body is in its prime from thirty to thirty-five; the mind at about forty-nine. The character of people in their prime is between that of the young and that of the elderly. Thus, people in their prime are neither overly confident nor overly timid, neither trustful nor mistrustful, and driven both by what is noble and by what is useful. ‘To put it generally, all the valuable qualities that youth and age divide between them are united in the prime of life, while all their excesses or defects are replaced by moderation and fitness.’
Source: Rhetoric, Book II, Chapters 12-14