Once in a while, I come across a gem of a post that I can file away to use in my teaching and advising, not to mention my constant struggle to think better and more productively as an economist (actually, in any area where I happen to be trying to think well). Here is one such gem, by Jeremy Kun. Enjoy! I am pretty sure you will find it enlightening even if (perhaps especially if) you are not thinking mathematically and consider those who do crushing bores. You’ve been warned!