“It is the mark of an educated mind to be able to entertain a thought without accepting it.”
From Aristotle?
Along the same lines: "Education is the ability to listen to almost anything without losing your temper or your self-confidence." -- Robert Frost
> entertain a thought without accepting it
Entertaining an idea is understanding it. And, there is some research to show that understanding an idea is believing it. Hence, understanding an idea and not believing it is very effortful.
[1] https://bear.warrington.ufl.edu/brenner/mar7588/Papers/gilbe...