I Admit It: Mathfolk Are Weird

[stoutfellow]

Had you been in the main office of the math department yesterday morning, you might have observed the following scene, as I and one of my colleagues discussed whether a certain thing was possible.

I held out my left arm straight in front of me, palm vertical, and said "One two".
I crossed my left arm with my right, palm also vertical, at about a sixty-degree angle: "One three".
I dropped my right arm, turned my left palm horizontal, and slashed my left arm across horizontally: "Four five".
My colleague nodded and grunted agreement.