To be added, with links to existing articles, especially the Diogenes Laertius comment to this effect.
KEY Texts:
Diogenes Laertius: "The internal sensations they say are two, pleasure and pain, which occur to every living creature, and the one is akin to nature and the other alien: by means of these two choice and avoidance are determined." (Bailey)
FAQ:
Glossary - What is the Epicurean Definition of "Pleasure?"
Articles:
On Pain, Pleasure, and Happiness
Discussions:
Feeling: The Faculty of Pleasure and Pain
