"Happiness is prior to being tranquil"-Is this right?
IV: In terms of the conceptual hierarchy, it's not right. "Happiness" is at the top, as the ultimate goal. Tranquillity is below it.
In practice, they happen at the same time. Happy people are also tranquil. Which is why we sometimes see tranquility equated with happiness.
There is also a certain degree of fuzziness in these words, and only when we talk about the conceptual hierarchy greater precision is usually needed. As an Epicurean I don't usually use "tranquility" because it is so fuzzy...
Cassius Amicus
I agree with IV's answer, and would add my personal opinion about the key words in the sentence:
"Happiness" - I believe in Epicurean terms this means "living pleasurably," which can be done in innumerable ways, since there are so many mental and physical possibilities in life. Epicurean happiness is to be contrasted with Arisotelian happiness, which requires much more than pleasure and ends up requiring many types of social and economic goods. It should also be contrasted with Platonic and Stoic happiness, which end up being a rigid and formal set of abstract principles - "virtue," in their terms. And of course you can carry the analogy much further and point out that religions define happiness as serving god, etc. So any discussion of happiness has to first define the word happiness.
"Tranquil" - I believe the focus of meaning here is on "smooth" and "uninterrupted," so that "tranquil" is best seen as an adjective describing the best way to experience pleasure/happiness, rather than as a independent state by itself. "Yellow" cannot be separated from "things that appear yellow." Yellow is neither an ideal form, in Platonic terms, nor an "essence" in Aristotelian terms. So as with "yellow," I don't think "tranquil" describes an independent separate state either. Neither tranquility nor "yellow" exist in the air. Yellow is an attribute of specific things that we perceive in the light to be yellow, and tranquility is an attribute of experiencing specific mental and physical activities smoothly and without disruption. There is no tranquility in death. Personally, I think "aponia" (absence of pain) is in the same category as tranquility. In Epicurean texts, painlessness seems to describe the state of experiencing pleasures (any number or type) **without any pain accompanying that experience.** Neither "tranquility" nor "painlessness" tell you anything about the positive state of what your mind or body are doing - those words simply tell you that whatever you are doing is not accompanied by disruption/turmoil or pain.
"Prior to" - Given the way I've described happiness and tranquility, ranking happiness and tranquility (or painlessness) on the same scale would be like ranking "oranges" (the fruit) with "things that are orange" (the color). "Tranquility" and "painlessness" are not complete states in themselves, but ways of describing the purest experience of pleasure: The purest experience of pleasure (any kind of pleasures) is when pleasures are experienced without disruption/turmoil and without pain.