Circular reasoning

Circular reasoning, or in other words, paradoxical thinking, is a type of formal logical fallacy in which the proposition to be proved is assumed implicitly or explicitly in one of the premises. For example:

"Only an untrustworthy person would run for office. The fact that politicians are untrustworthy is proof of this."

Such an argument is fallacious, because it relies upon its own proposition — "politicians are untrustworthy" — in order to support its central premise. Essentially, the argument assumes that its central point is already proven, and uses this in support of itself.

Circular reasoning is different from the informal logical fallacy "begging the question", as it is fallacious due to a flawed logical structure and not the individual falsity of an unstated hidden co-premise as begging the question is.

See also

• Argument from authority
• Coherentism
• I'm entitled to my opinion
• Self-reference
• Tautology (rhetoric)