Circular reasoning
The conclusion is hiding inside the premises.
Fallacy vs. flaw, on this site. Our fallacy page on begging the question teaches the general form. This page is the LSAT version: Flaw questions phrase the right answer as "the argument assumes what it sets out to prove" or "the premises presuppose the truth of the conclusion." Same error, test-day wording.
Start with the general version: the fallacy page. Then come back here for the test-day version.
What it is
Circular reasoning happens when the evidence for a conclusion just restates the conclusion in different words. The argument goes in a circle: believe X because of Y, and Y is just X again.
It is hard to spot because the restatement is usually disguised with synonyms or a longer sentence. Strip the argument to its skeleton and the circle shows.
An LSAT-style example
This example is original. It is not a real LSAT question.
This novel deserves the award because it is the most award-worthy book published this year.
The flaw: "Deserves the award" and "most award-worthy" are the same claim. The premise gives no independent reason, so nothing has actually been argued.
How to spot it on test day
- Ask: if I delete the fancy words, does the premise say anything the conclusion does not already say?
- Watch for conclusions about quality, worth, or truth supported by synonyms of the same quality, worth, or truth.
- Definitions offered as arguments are a common disguise: "X is Y because X meets the definition of Y."
The right answer vs. the trap
The right answer
Usually "presupposes the truth of what it is trying to establish" or "the argument is circular."
The trap
"The argument uses vague language." Vagueness is not the problem here. The problem is that the reasoning goes nowhere.
Find your weak flaws
The free diagnostic scores flaw questions separately and shows whether this pattern is costing you points.