Full Idea
Every science performs its function well only when it observes the mean.
Clarification
Here 'science' is the Greek word 'techné', also translated as 'skill'
Gist of Idea
Skills are only well performed if they observe the mean
Source
Aristotle (Nicomachean Ethics [c.334 BCE], 1106b09)
Book Reference
Aristotle: 'Ethics (Nicomachean)', ed/tr. ThomsonJ A K/TredennickH [Penguin 1976], p.100
A Reaction
Hm. Not sure what he has in mind. Most people aspire to perfection in their skills. The mean needs a continuum between two obvious extremes.