After extensive and mostly-fruitless investigation, I’ve finally found some tangible evidence of that oft-alleged connection between the “universalism” of Christianity and the homogenous, egalitarian conception of humanity. In the Middle Ages, the Church defended – against the popular tradition that monstrous births were suppositious and/or the result of bestiality – the thesis that grossly deformed infants were every bit as human as healthy babies and thus needed baptism and so on.
As a purely scientific question, the medieval clergy hit this one out of the park. All appearances to the contrary, grotesque children are specimens of H. sapiens, and their disfiguring syndromes are the result of genetic defects rather than interspecies mésalliance. However, it is extremely difficult to find pre-modern examples of Christian authorities deducing the biological equality (and equal dignity) of empirically disparate human beings a priori from metaphysical principles; in the case of monstrous births, we have at least one. (But as Dissident Sociologist is fond of noting, Stoicism is still a much better match for the universalist strain in progressive ideology.)