It's the week before spring break, and that means midterm exams for everybody. Luckily I only have one midterm, but unluckily it's in class about theoretical handwaving as opposed to the class about writing programs that make cool pictures. So I've been studying my handwaving technique today in preparation, including my favorites: proof by strong statement, proof by repetition, and proof by writing "Q.E.D." at the end of a nonsensical paragraph.

My main issue with proofs is that, to quote Homer Simpson, you can "use them to prove anything that's even remotely true". It's easy to put a lot of mathematical-looking statements in there and hope that your reader gets lost on the way to stating your conclusion. Drop in enough Sigmas, Unions, and random Greek letters, and either I'll lose track of what you're saying or I'll fall asleep. A sufficiently long mathematical proof could convince me that 1 + 1 is 73, Shakespeare was actually a collection of 100 processors in parallel running a distributive writing algorithm, or St. Louis has a tropical climate.

And often we're asked to prove things that seem obvious. Think about how you would write a proof that 2 + 2 = 4, for example. The correct answer is: "it just is, dammit!", but I have a feeling that if I wrote this on my test, then I would get to see the proof that 100 - 20 = 80 (each problem is worth 20 points).

I much prefer reasoning things out in an English paragraph. Then it's easy to see when someone makes a wild leap of logic, so you know if their proof is sound or not. If you said, for instance, "Jared weighed 350 pounds, then Jared started eating Subway sandwiches and exercising every day, after one year Jared weighed 200 pounds, therefore Subway sandwiches are a great way for everyone to lose weight", it's easy to see the problems:

-Not only did Jared start eating Subway, but he also stopped eating other junk foods. Maybe this had something to do with his weight loss.
-Jared also started exercising. Maybe this had something to do with his weight loss.
-"Jared" cannot be extrapolated into "everyone". For some people, eating Subway sandwiches every day would probably cause them to gain weight.
-Sandwiches made the way that Jared ate them (without cheese or any of the tasty breads) don't taste very good.

Q.E.D.