If not for Pythagoras -- that old, gray-bearded Greek philosopher and mathematician from 2,500 years ago -- students today would still be hunched over their geometry homework, wondering how to draft a proof for the area of a right triangle.
Good ole Pythagoras. Now he was a man of rational-thinking and logic, one might say.
He also, around 540 B.C.E., led a cult of other mathematicians known as the Pythagoreans in séance rituals which involved our earliest documented accounts of Ouija-like boards:
A mystic table, moving on wheels, moved towards signs, which the philosopher and his pupil, Philolaus, interpreted to the audience as being revelations supposedly from an unseen world.
Logic obviously did not govern all of his actions.