In logic, a proposition may be a truism even if it is not a tautology, a restatement of a definition, or a theorem derived from axioms that are generally held to be true. In fact, some would say that such analytic propositions should not be regarded as truisms.

In philosophy, a sentence which asserts incomplete truth conditions for a proposition may be regarded as a truism. An example of such a sentence would be: "Under appropriate conditions, the sun rises." Without contextual support — a statement of what those appropriate conditions are — the sentence is true but uncontestable. A statement which is true by definition ("All cats are mammals.") would also be considered a truism.

Often the word is used to disguise the fact that a proposition is really just a half-truth or an opinion, especially in rhetoric.

Examples

• Some versions of the Anthropic principle, which states that any valid theory of the universe must allow for humans to exist also.

See also

• Aphorism
• Axiom
• Cliché
• Commonplace
• Contradiction
• Dictum
• Fact

• Figure of speech
• Gospel
• Jacques de la Palice
• Maxim
• Moral
• Synthetic proposition
• Tautology