Thank you for your comment! I believe that you are right in cases where such opposites are assumed to exist. Specifically for Epicurus, though, this is not the case, since he defines happiness to be the absence of pain. For him there is only pain (of the body, or of the soul), and the absence of pain (which is complete happiness). So if we wanted to see a continuum between two extremes, this would purely be a continuum of pain, from maximum pain to zero pain (which is happiness for Epicurus). Of course, as you say, this is too simplistic (even more so actually than having two opposite poles). But that’s Epicurus. Part of his program is to rid people of the anxiety that they experience because they are afraid to miss on possible pleasures. This fear, he thinks, drives them into lives full of unpleasant experiences (hard work, mortgages, credit cards). But if we buy his premise that just the absence of pain is already complete pleasure, then we will need much less in order to be completely happy: just so much of material goods that will suffice to remove our pain (hunger, cold, etc). And then we would be at “peace.” (What the Greeks actually called ataraxia, literally: non-disturbance).

Many thanks again for your insightful comment!