Thanks for that analysis Todd. Yes these are the issues I am talking about.
I think the point that hit me today as important to address is what I think is a common perception: that Epicurus held that "justice" equates to "agreements not to harm and be harm." If we look at that very simplistically, then it would be easy for someone to say that once in that agreement, it is "unjust" to leave it.
But it seems to me the clear thrust of 37 and 8 is to emphasize exactly that people WILL not only occasionally but frequently go in and out of such agreements, with the temporary nature of them being the exception and not the rule.
So what then "is," or what "does it mean" for a thing to be "unjust." Is "injustice" really anything at all other than the perception that some person or group will be out to punish you for the action?
Maybe I am overthinking this, but my perception is that people who address these PD's at all treat them superficially and conclude that Epicurus held non-aggression compacts to be "good/just" and exiting from non-aggression pacts to be "bad/unjust" and I am thinking that such a deduction about Epicurus would be way off the mark.
I think Epicurus would agree with your criticism of common perceptions of the "social contract" theory, and that the extensive discussion of justice may be intended to emphasize the point that is clear elsewhere -- that "virtue" (any form of virtue, including "justice") really has no intrinsic meaning whatsoever divorced from the question of what pain and pleasure results from it.
In our Skype discussion today it was pointed out that "justice" may be somewhat unique as being traced to "anticipations," and that we have direct "feelings" of justice and injustice, but I am not sure both those observations don't apply to each and every concept that we fit within "virtue."
At any rate this is a subject that we haven't talked about very much, but it's one that I don't think should be considered off topic in the sense of normal day-to-day political issues. What we are talking about here is the more fundamental issue of even how to begin to analyze social relations of any kind; we're not criticizing or praising any particular form of social relation.