Earlier quoted context omitted.
Sound arguments from faulty premises are still sound arguments – but identifying whether premises are valid is hard . My heuristic, "if a sound argument concludes that racism is true, there's something wrong with the premises", is pretty effective in telling me where to look, but doesn't eliminate the hard work of distinguishing truth from falsehood. That this heuristic has never failed doesn't actually prove that al…
Well, take racism out of it. Do a thought experiment. Take a genetically identical starting population with identical culture, customs, etc. Split them onto two islands, island A and island B. Island A has temperate weather, plentiful food, resources, and no natural predators. Island B has natural disasters, brutal seasons, intermittent food shortages, etc. Check back in on both populations (assuming they lived exclu…
Would all these various effects cancel each other out, leaving no phenotypical variation except skin colour (due to the selective effects of melanoma and vitamin D deficiency), and no significant psychological differences except those caused by unselected genetic drift, which are utterly erased by the first generation of interbreeding? There is no way to tell, from the information you have provided. Your thought experiment reveals your (and my) own biases, nothing more. Thought experiments only work in mathematics and physics, not (except in extremely simple situations) evolutionary biology.