F039 • Informal - Presumption
Also known as: Petitio Principii, Circular Reasoning, Circular Argument
We reach for an argument to support what we believe, and without realizing it, we build the conclusion into the starting point. The argument goes in a circle -- it assumes the very thing it is trying to prove -- but it can feel like solid reasoning because the conclusion and the premise are dressed in different words.
Loading examples...
We reach for reasons to justify what we believe, and that instinct is healthy -- it is the beginning of all reasoning. The trouble starts when the reason we find is really just the belief itself, restated. If someone says a law is good because it is beneficial, they have not actually given a reason; they have said the same thing twice in different language. This can be surprisingly hard to catch, because our minds are very good at recognizing that two statements agree and very bad at noticing when that agreement is trivial. The tighter the circle, the harder it is to spot. When the premises and the conclusion are separated by several steps, the circularity can be almost invisible -- each link in the chain seems to add something new, but the whole thing loops back to where it started without ever touching independent evidence.
| Defining terms is not circular reasoning, even though it can look similar on the surface. Saying 'a bachelor is an unmarried man' is a definition, not an argument. The trouble starts when a definition is smuggled in as if it were evidence for a separate claim. |
| Sometimes restating a point in different words is genuinely useful for communication -- for clarity, for emphasis, for making sure someone understands. The pattern becomes a problem when restatement masquerades as justification. |
| You might notice that an argument feels airtight in a way that is almost too easy -- no part of it creates any tension or surprise. That frictionlessness can be a sign that the conclusion was baked in from the start. |
| Try restating the premise and the conclusion side by side in your own words. If they say the same thing, the argument is circular. |
| Watch for moments when someone is asked 'why?' and their answer is just a restatement of the original claim in more elaborate language. The elaboration can make it feel like new information when it is not. |
| Ask yourself: if I did not already believe the conclusion, would these premises give me a reason to start? If the premises only make sense to someone who already accepts the conclusion, the argument may be going in a circle. |
| Notice when a chain of reasoning feels like it is making progress but keeps arriving back at the same place. Wide circles -- where A supports B, B supports C, and C supports A -- are harder to spot but follow the same pattern. |
| Confusing circular reasoning with deductive validity. All valid deductive arguments have conclusions that are in some sense 'contained' in their premises -- that is what makes them valid. The difference is that a good deductive argument brings together multiple independent premises; a circular argument uses the conclusion itself as a premise. |
| Missing wide circles. When the loop goes through several intermediate steps, each step can look like it adds something new. The circularity only shows up when you trace the chain all the way back to the beginning. |
| Treating every definition-based argument as circular. Defining your terms is not the same as begging the question. The fallacy arises when the definition is doing the work of an argument -- when it is being used to prove something rather than to clarify what you mean. |
| Begging the Question |
|---|
| Assuming the truth of the conclusion in the premises. The argument is circular: it presupposes what it aims to prove. |
| An argument should provide independent reasons for the conclusion. If the conclusion is assumed in the premises, the argument provides no new justification. |
Hover to see definition, click to view full details