Full Idea
It is by preserving the mean that arts produce everything that is good and beautiful.
Clarification
Here 'arts' is the Greek word 'techné', also translated as 'skill'
Gist of Idea
The arts produce good and beautiful things by preserving the mean
Source
Plato (The Statesman [c.356 BCE], 284b)
Book Reference
Plato: 'Statesman', ed/tr. Bernadete,Seth [University of Chicago 1986], p.35