In classical rhetoric and logic, begging the question or assuming the conclusion (Latin: ) is an informal fallacy that occurs when an argument's premises assume the truth of the conclusion. Historically, begging the question refers to a fault in a dialectical argument in which the speaker assumes some premise that has not been demonstrated to be true. In modern philosophical usage, it has come to refer to an argument in which the premises assume the conclusion without supporting it. This makes it an example of circular reasoning.

Some examples are:

  • “Wool sweaters are better than nylon jackets as fall attire because wool sweaters have higher wool content".
  • The claim here is that wool sweaters are better than nylon jackets as fall attire. But the claim's justification begs the question, because it presupposes that wool is better than nylon. An essentialist analysis of this claim observes that anything made of wool intrinsically has more "wool content" than anything not made of wool, giving the claim weak explanatory power for wool's superiority to nylon.
  • "Drugs are illegal, so they must be bad for you. Therefore, we ought not legalize drugs, because they are bad for you."

In modern times, "beg the question" has taken on the common meaning of "strongly prompt the question", a usage distinct from the study of logic. This usage is criticized for diluting the original meaning of the phrase.

History

thumb|upright|Bust of [[Aristotle, whose Prior Analytics contained an early discussion of this fallacy]]

The original phrase used by Aristotle from which begging the question descends is , or sometimes , . Aristotle's intended meaning is closely tied to the type of dialectical argument he discusses in his Topics, book VIII: a formalized debate in which the defending party asserts a thesis that the attacking party must attempt to refute by asking yes-or-no questions and deducing some inconsistency between the responses and the original thesis.

In this stylized form of debate, the proposition that the answerer undertakes to defend is called () and one of the rules of the debate is that the questioner cannot simply ask (beg) for it (that would be trivial and uninteresting). Aristotle discusses this in Sophistical Refutations and in Prior Analytics book II, (64b, 34–65a 9, for circular reasoning see 57b, 18–59b, 1).

The stylized dialectical exchanges Aristotle discusses in the Topics included rules for scoring the debate, and one important issue was precisely the matter of asking for the initial thing—which included not just making the actual thesis adopted by the answerer into a question, but also making a question out of a sentence that was too close to that thesis (for example, PA II 16).

The term was translated into English from Latin in the 16th century. The Latin version, , can be interpreted in different ways. (from ), in the post-classical context in which the phrase arose, means or , but in the older classical sense means , or . , genitive of , means , or (of an argument). Literally means or .

The Latin phrase comes from the Greek ( ) in Aristotle's Prior Analytics II xvi 64b28–65a26:

Aristotle's distinction between apodictic science and other forms of nondemonstrative knowledge rests on an epistemology and metaphysics wherein appropriate first principles become apparent to the trained dialectician: