Full Idea
In each one of us there are two ruling and impelling principles: a desire for pleasure, which is innate, and an acquired conviction which causes us to aim at excellence.
Clarification
'Virtue' here is the Greek word 'areté', which also translates as 'excellence'
Gist of Idea
The two ruling human principles are the natural desire for pleasure, and an acquired love of virtue
Source
Plato (Phaedrus [c.368 BCE], 237d)
Book Reference
Plato: 'Phaedrus and Letters VII and VIII', ed/tr. Hamilton,Walter [Penguin 1973], p.36
A Reaction
This division is too neat and simple. An obsession with pleasure I would take to be acquired. If you set out to do something, I think there is an innate desire to do it well.