Great post Menno! My only quibble is with the discussion of emergence as the justification for reasoning in terms of aggregates. Unless we draw the kinds of distinctions you have so concisely laid out elsewhere in your post, this seems again to pose the danger of needlessly conflating ontological and epistemological issues. There may be scant profit in debating whether some exploitable aggregate regularity is "truly" emergent. I would argue that the core justification is pragmatic. If I want to buy a car, I do not find it useful to ponder the molecular constitution of the salesman. If I want to predict the stock price of a large firm, I do not seek information about the lives of the employees. If I want to think about the Sunni insurgency, I do not use the fact that Iraq is full of individuals as an excuse to ignore that fact that Iraq is full of tribes and clans, which have proved to be important *actors* in the conflict. Cheers, Alan Isaac