Christian Miller is arguing that while we do have phycological character traits and motivations, that persist between situations, how we actually behave is a complex interaction between these and our contexts. Divergence can maybe be explained as much by contexts as by characteristics. If I were to meet someone who works a similar job, has a similar social and familia situation, but divergent motivations, I might have more in common with them than I would have if I met the university student version of myself.