Definition · Plain-language
Circular reasoning
Circular reasoning is a fallacy in which an argument’s conclusion is already assumed by one of its premises, so it proves nothing.
The step most authors miss
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Why it proves nothing
A good argument supports its conclusion with premises that are independently acceptable. Circular reasoning fails this test because the truth of the premise already presupposes the truth of the conclusion. "The Bible is true because it is the word of God, and we know it is the word of God because the Bible says so" assumes precisely what it sets out to prove. The reasoning may be valid in the narrow sense that the conclusion follows, yet it persuades no one who does not already accept the conclusion, so it has no probative force.
Relation to begging the question
Circular reasoning is the broad term; begging the question (Latin petitio principii) is the classical name for the same flaw — assuming as a premise the very point at issue. Modern usage often treats them as interchangeable. Note that "begging the question" is frequently misused to mean "raising the question"; in logic it means assuming the conclusion. The circle can be tight, restating the conclusion as a premise in different words, or wide, looping through several steps before returning to the starting assumption.
Spotting the loop
To detect circular reasoning, identify the conclusion and then check whether any premise could only be accepted by someone who already believes that conclusion. If so, the argument is circular. A useful test is to ask whether the premise gives an independent reason — evidence or grounds that stand apart from the conclusion. Subtle circularity often hides behind synonyms or technical restatement, so paraphrasing each premise in plain terms and comparing it with the conclusion helps reveal whether the argument is genuinely going in a circle.
Key facts
At a glance
- Definition: the conclusion is assumed within the premises
- Type: informal fallacy (of presumption)
- Latin name: petitio principii (begging the question)
- Key flaw: premises offer no support independent of the conclusion
- Common confusion: "begs the question" ≠ "raises the question"
- Test: does any premise presuppose the conclusion is already true?
Common misconceptions
What people often get wrong
Often heard: Circular reasoning is invalid, so the conclusion is automatically false.
Actually: Circular arguments are often technically valid — the conclusion does follow from a premise that restates it. The flaw is not invalidity but lack of support: the argument gives no independent reason to accept the conclusion, whether or not that conclusion happens to be true.
Often heard: "Begging the question" means prompting an obvious follow-up question.
Actually: In logic, begging the question means assuming the conclusion within the premises — it is a synonym for circular reasoning. The popular sense of "raising a question" is a different, non-logical usage. Precise writing keeps the two apart.
Often heard: Repeating yourself is the only way an argument can be circular.
Actually: Circularity need not be a blunt restatement. A wide circle can loop through several plausible-looking steps before quietly relying on the original conclusion as a premise. Detecting it requires tracing whether the support ultimately depends on what was to be proved.
Going deeper
