Circular Reasoning
Using your conclusion as your premise - the argument proves itself by assuming itself.
Also known as: begging the question, circular logic, petitio principii, tautological reasoning
What it means
Circular reasoning is a logical fallacy in which the conclusion of an argument is assumed in one of its premises. The argument goes in a circle: A is true because of B, and B is true because of A. It can feel convincing in the moment because every step in the chain appears to follow logically from the one before - but the chain forms a loop, with no independent support at any point.
The classic example: “The Bible is the word of God. We know this because the Bible says so, and the Bible is always truthful because it’s the word of God.” Each claim supports the other, but neither is supported by anything outside the circle. If you don’t already accept the conclusion, the argument gives you no reason to start.
Circular reasoning is often harder to spot than this example suggests, because in real conversations the circle is usually large enough that by the time the argument returns to its starting point, you’ve forgotten where it began. The more words and steps involved, the less obviously circular it feels.
In the real world
In politics, circular reasoning often hides inside appeals to institutional authority. “We can trust the government’s assessment because it was produced by qualified experts. How do we know they’re qualified? Because the government appointed them. Why should we trust the government’s appointments? Because they use qualified experts.” The circle can spin indefinitely without ever touching external evidence.
Conspiracy theories are frequently circular. “The lack of evidence proves the conspiracy, because a really good conspiracy would leave no evidence.” The theory is unfalsifiable - any evidence against it is absorbed as evidence for it. The conclusion is baked into the starting assumptions, so no possible observation could challenge it.
In everyday arguments, circularity often sounds like: “I deserve the promotion because I’m the best person for the role.” “Why are you the best person?” “Because I’m the one who should be promoted.” Or in relationship conflicts: “I don’t trust you.” “Why not?” “Because you do untrustworthy things.” “Like what?” “Like things that make me not trust you.” The argument feels like it’s going somewhere but it’s walking in a circle.
How to spot it
Rephrase the argument as a simple chain. If the end point is also the starting point - if the 'proof' requires you to already accept the conclusion - you've found circular reasoning. The giveaway is that the argument cannot be disagreed with on its own terms, because it's defined its way out of challenge.
The thought to hold onto
An argument that proves itself is an argument that proves nothing.