So, your statement about pre-modern thought being rational but based on dubious premises really made me think - thanks. Though we probably like to view our age as a sort of Reason Renaissance, it is likely that there are significant biases in the foundation of our reasoning - call them flaws, perhaps.

It’s seems to be quite usual for humans in all periods to treat various kinds of out-groups as less than human. It’s not necessarily limited to human culture either. There’s some evidence that chimps can treat out-groups more like a different species.

What an interesting thought about the possibility that people disabled in the area of speech were perceived as less than human. The legendary pathos of the village idiot springs to mind here: the image of a being that is helpless without the charity of others, like a stray animal. This is yet another reason for my ticklist of why it is better to be alive in this century and view the lessons of history from a safe perch.