Epicurus (341 - 270 B.C.E.) was an ancient Greek philosopher and founder of the school of philosophy called Epicureanism.
On pleasure:
As soon as each animal is born, it seeks pleasure and rejoices in it as the highest good, and rejects pain as the greatest bad thing. No one rejects or avoid pleasure itself just because it is pleasure and no one choose pain over pleasure just because it is pain. Thus, pleasure is the first natural good, while pain is the first natural evil.
On happiness:
Happiness, the greatest pleasure, is the state of the soul that is free of disturbances and the state of the body that is free of pain. Hence, to attain happy life, we need to strive for an absence of both mental and physical pain.
