One of my favorite passages in Lucretius (to which Cassius alludes, I think, above) talks about the explanations of human dispositions and behaviors at the atomic level (DRN 3: @310, attached). This is one of those great Epicurean science passages, actually, because it's like, 'trust me, there's a physical explanation. I just can't give it to you here, but it's definitely physical.' I find it interesting that he says we can change, but never entirely--some things can't be erased. As for the effe…