In contemporary usage, "begging the question" often refers to an argument where the premises are as questionable as the conclusion.
In popular usage, "begging the question" is often used to mean that a statement invites another obvious question. This usage is disparaged. "Raises the question" may be appropriate.
Begging or assuming the point at issue consists (to take the expression in its widest sense) in failing to demonstrate the required proposition. But there are several other ways in which this may happen; for example, if the argument has not taken syllogistic form at all […]. If, however, the relation of B to C is such that they are identical, or that they are clearly convertible, or that one applies to the other, then he is begging the point at issue.
Fowler's Deductive Logic (1887) argues that the Latin origin is more properly Petitio Quæsiti which translates as "begging the question."
Although these statements have a logical form, they do nothing to convince one of the honesty of the speaker because the matter (that is, what the words actually symbolize) of the major premise (that Paul believes what he says) and the conclusion are actually the same thing. The speaker is stating a tautology "If Paul believes what he says, then Paul is not lying".
Another common instance is found when computations lead to identities: someone is trying to solve an equation and in the course of the attempt reduces a mathematical expression to itself. The general process of solution might be legitimate, but its application to the particular question is incorrect.
Such arguments are formally logical. That is, the conclusion does formally follow; however, since it is materially identical to the major premise, the argument is said to be materially invalid. All self-circular arguments have this characteristic: that the proposition to be proved is assumed at some point in the argument.
Formally speaking, the fallacy of petitio principii has the following structure: For some proposition p,
The syntactic presentation of the fallacy is rarely this transparent, as is shown, for example, in the above argument purportedly proving Paul is telling the truth.
A specific form of this is reducing an assertion to an instance of a more general assertion which is no more known to be true than the more specific assertion:
If the first premise is accepted as an axiom within some moral system or code, this reasoning is a sound argument against the death penalty. If not, it is in fact a weaker argument than a mere assertion that the death penalty is wrong, since the first premise is stronger than the conclusion.
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:
Fowler's Modern English Usage classifies begging the question in a similar fashion (for example, in contrast to the meanings from Merriam-Webster, the Oxford English Dictionary, and the American Heritage Dictionary). 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."
In a related sense, the phrase is occasionally used to mean "avoiding the question". Those who use this variation are explaining that the argument lacks a premise, and they have missed the self-circularity of the argument because of it.
Begging the question is also related to the fallacy of many questions — a fallacy more commonly known as "loaded questions", that is committed when a question presupposes something that has not been proven or accepted by all the people involved.
A possible origin for this confusion in usage is the likeness of the word "beg" to the word "beget", which can mean "to originate." The phrase "to beget the question" might have been confused in time with the similar-sounding (but very different) notion from logic "to beg the question". An example of this usage is found in An Enquiry Concerning Human Understanding by David Hume, published in 1748: "This begets a very natural question; What is meant by a sceptic?" (Section XII).
Another possible origin is that the situation is such that the most obvious question to be asked is the question given, as if the situation is anthropomorphically begging, or pleading, for the participants to ask the question. For example, "This year's budget deficit is half a trillion dollars. The most obvious question to ask is: how are we ever going to balance the budget?"
Arguments over such usage are an example of debate over linguistic prescription and description. As John McIntyre (copyeditor), Baltimore Sun assistant managing editor, puts it: "Writers who were not taught logic in school — evidently a great many — will think that 'to beg a question' means 'to give rise to a question.' In that they are like the multitude of writers who have appropriated technical but dimly understood language. A parameter, for example, is 'a constant, with variable values, used as a referent for determining other variables.' If you are a mathematician, that definition from Webster's New World College Dictionary probably means something to you. If you are not a mathematician, you are probably using parameter to mean a boundary or limit or guideline, or perhaps nothing in particular. People do write this way. Some even talk this way. Eventually, loose applications of technical terms to different contexts find their way into the dictionary, some embedding themselves in the language. That is fine. But in the interval, anyone who wishes to write precisely will be cautious.