In the “today I learned” department, I had heretofore had no idea that the phrase “begs the question” is a fallacy and should not be used. Here’s Wikipedia’s explanation:

Begging the question is one of the classic informal fallacies in Aristotle’s Prior Analytics. Some modern authors consider begging the question to be a species of circulus in probando (Latin, “circle in proving”) or circular reasoning. Were it not begging the question, the missing premise would render the argument viciously circular, and while never persuasive, arguments of the form “A therefore A” are logically valid because asserting the premise while denying the self-same conclusion is a direct contradiction. In general, validity only guarantees the conclusion must follow given the truth of the premises. Absent that, a valid argument proves nothing: the conclusion may or may not follow from faulty premises—although in this particular example, it’s self-evident that the conclusion is false if and only if the premise is false (see logical equivalence, logical equality and law of identity.

I know I’ve written dozens of papers in high school and college where I started a sentence with “Which begs the question, …” The proper alternative is “Which raises the question.”