Dehumanisation overturns our social instincts and conceives our fellow humans as unnatural beings. Combined with a perceived physical threat, this metaphysical transgression leads to atrocity writes David Livingstone-Smith

I have been studying dehumanization for the last fifteen years, and over that period my understanding of it has changed and deepened. Like most other researchers, I started out believing that when people dehumanize others, they think of them as subhuman animals—as rats, or cockroaches, or bloodthirsty predators. But I eventually came to recognize that this account isn’t quite right. Dehumanizers don’t think of their victims as nothing but animals. In the most dangerous kind of dehumanization—the kind that leads to the worst abuses and atrocities—dehumanizers conceive of their victims as monstrous, unnatural beings.

Here are a few examples. Medieval Christians represented Jews as demonic beings in league with the Devil. They were supposed to be skilled in the art of sorcery and were even equipped with horns and tails. It was said that kidnapped and ritually sacrificed Christian children to drain them of their blood which they mixed with matzah dough and gobbled up during the annual Passover meal. Muslims were also demonized. One medieval chronicler described them as “a fiendish race . . . deformed by nature and unlike other living beings, black in color, of enormous stature and inhuman savageness.” During the Jim Crow era American racists depicted Black men in similar terms as “the most horrible creature upon the earth, the most brutal and merciless . . . a monstrous beast, crazed with lust. His ferocity is almost demoniacal.” Nazi propaganda presented Jews as nightmarish, malevolent entities. For example, one tract entitled Der Untermensch (“the subhuman”) states of Jews that: