On Thursday, June 21, 2012 I heard Dennis Prager on his nationally-syndicated radio show use 'beg the question' when what he meant was 'raise the question.' This is a very common mistake nowadays.
I correct Mr. Prager because I love him.
The visage of Jeff Dunham's 'Walter' signals that a language rant is in the offing should you be averse to such things.
To raise a question is not to beg a question. 'Raise a question' and 'beg a question' ought not be used interchangeably on pain of occluding a distinction essential to clear thought. To raise a question is just to pose it, to bring it before one's mind or before one's audience for consideration. To beg a question, however, is not to pose a question but to reason in a way that presupposes what one needs to prove.
Suppose A poses the question, 'Does Allah exist?' B responds by saying that Allah does exist because his existence is attested in the Koran which Allah revealed to Muhammad. In this example, A raises a question, while B begs the question raised by A. The question is whether or not Allah exists; B's response begs the question by presupposing that Allah does exist. For Allah could not reveal anything to Muhammad unless Allah exists.
The phrase 'beg the question' is not as transparent as might be hoped. The Latin, petitio principii, is better: begging of the principle. Perhaps the simplest way to express the fallacy in English is by calling it circular reasoning. If I argue that The Los Angeles Times displays liberal bias because its reportage and editorializing show a left-of-center slant, then I reason in a circle, or beg the question. Fans of Greek may prefer hysteron proteron, literally, the later earlier. That is, what is logically posterior, namely, the conclusion, is taken to be logically prior, a premise.
Punchline: Never use 'beg the question' unless you are referring to an informal fallacy in reasoning. If you are raising, asking, posing a question, then say that. Do your bit to preserve our alma mater, the English language. Honor thy mother! Matrix of our thoughts, she is deeper and higher than our thoughts, their sacred Enabler.
Of course, I am but a vox clamantis in deserto. The battle has already been lost. So why do I write things like the above? Because I am a natural-born scribbler who takes pleasure in these largely pointless exercises.
And perhaps there is a bit of virtue-signaling going on.