Plato's Socrates is very reminiscent of this, isn't he? His whole shtick is essentially insisting that he's a person of the sort we'd put on the left side of the curve.

https://en.wikipedia.org/wiki/I_know_that_I_know_nothing gives as illustration a quote from the Apology:

"I seem, then, in just this little thing to be wiser than this man at any rate, that what I do not know I do not think I know either", also translated as "[...] I am better off than he is – for he knows nothing, and thinks he knows. I neither know nor think I know."

It isn't carved the same way as in the Pascal quote so it may not fully count—though someone might make a better case that it does—but in contrast to knowing, there's definitely 'doesn't know but thinks he knows' (your midwit) and 'doesn't know and doesn't think he knows' (himself).

(Major bonuses for Aristotle; Shakespeare would also be legit)