Full Idea
When harmony is being restored, and the natural state of harmony is approached, then pleasure arises.
Gist of Idea
We feel pleasure when we approach our natural state of harmony
Source
Plato (Philebus [c.354 BCE], 31d)
Book Reference
Plato: 'Philebus', ed/tr. Waterfield,Robin [Penguin 1982], p.86
A Reaction
The supreme value of harmony was important to Plato, but most of us are less convinced, I suspect. The way to achieve harmony is to avoid anything stressful.