In other words we can't wait forever debating "what does happiness mean." We have to decide NOW whether our goal is happiness, or obeying the gods, or being "rational," or being a "good person," or whatever. So I think it's a mistake to think that we have to know all there is to know about the etymology of happiness before we decide how to organize our lives.
Cassius ,
Thanks for the Claude (AI) bibliography, which I am finding most thorough and helpful. To answer your key question, "what is happiness", I agree that we cannot afford to wait for perfect clarity before we must act to implement Epicurean principles.
We face choices every moment, every day; so I don't find this question as merely academic. We must choose whether to organize our lives around the pursuit of happiness, or around obedience to divine will, or around abstract rationality, or around virtue as an end in itself?
If I understand correctly, Epicurus gave a clear principle: examine your desires, distinguish the necessary from the unnecessary, and pursue what genuinely produces peace of mind and freedom from pain. This is a guide for healthy living now.
The real question becomes: will we trust the guidance nature has given us, or will we defer to external authorities? As I develop trust in nature's guidance, the path forward becomes clearer. And I find the guidance from studying the Epicurean principles, provides examples and advice on how to focus honest attention on what produces genuine tranquility in our lives and what disturbs it. This seems to be a good path for pursuing a life of well-being.