I think the book is very coherent in terms of its theme. Diamond keeps hammering away at the same point over and over, right? It's all about geography, geography, geography. That's what the first part of the question means. As far as the second part goes, I would say yes. At least he has for me. But the problem is that you either believe him or you don't -- there's no way to prove for sure that culture or race didn't play into European dominance. So I think he makes a good case, but I'm already inclined to think that way anyway. If I believed that culture mattered, I'm not sure I'd be convinced by what he says because there's not really (and can't really be) any solid evidence that absolutely proves culture was irrelevant.