I don't think that hideous things, like eugenics or Nazi racism, happen because of a lack of understanding. They happen because people have their heads up their

I don't think that hideous things, like eugenics or Nazi racism, happen because of a lack of understanding. They happen because people have their heads up their butts with megalomaniac ideas about the world and their place in it. The "Master Race" was not a misunderstanding, it was some people wanting to be better than everyone else and making up, out of whole cloth -and no empirical evidence at all- that they were. There certainly wasn't universal consensus about it btw, just between Nazis. I agree that there are dangers in trusting consensus as a mechanism for advancement of knowledge, and I see your point about risking losing focus on the border. But I think it is also very important to have a common body of knowledge that we can all agree on. Take flying again: nobody disputes the fact that planes are flying (again, nobody who isn't just being contrary). We can work out the gray areas in time and they don't necessarily make progress impossible. E.g. maybe we can't agree on whether hovercrafts fly, but we can still make them and use them. So there is a limiting effect, like I point out in my other comment, but it is not a hard lock on progress. And I think that avoiding endless philosophical discussions is a big advantage. If there is a better heuristic then I'm happy to embrace it btw. But, is there?