Question begging from wikipedia

AI's notepad has a discussion on Question begging well let's go straight to the encyclopedia....

John Woods categorizes "begging the question" more generally, as:

Let T be a thesis advanced by Smith. Let A be a proposition forwarded by Jones as counting against T. Then Jones begs the question against Smith’s thesis T if:

• A is damaging to T,
• A is not conceded by Smith, does not follow from propositions already conceded by Smith, and
• is not otherwise ascribable to Smith as what we might call a “reasonable presumption” or a “default” (for example, the belief that water is wet or that Washington is the capital city of the United States).

Fowler's Modern English Usage classifies begging the question in a similar fashion... Fowler states that it is "The fallacy of founding a conclusion on a basis that as much needs to be proved as the conclusion itself."

And in the more formal section

"when a circular argument is used within one syllogism. That is, when the deduction contains a proposition that assumes the very thing the argument aims to prove... For example here is an attempt to prove that Paul is telling the truth:

• Suppose Paul is not lying when he speaks.
• Paul is speaking.
• Therefore, Paul is telling the truth.

Although these statements have a logical form, they do nothing to convince one of the truthfulness of the speaker because the matter (that is, what the words actually symbolize) of the major premise (the general supposition Paul does not lie when he speaks) and the conclusion are actually the same thing. In seeking to prove Paul's truthfulness, the speaker asks his audience to assume that Paul is telling the truth, so this actually "proves" the tautology "If Paul is not lying, then Paul is telling the truth."