Truism
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A truism is a claim that is so obvious or self-evident as to be hardly worth mentioning, except as a reminder or as a rhetorical or literary device.
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 contentless.
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
- In logic: "A AND NOT A is a contradiction".
- In set theory: a branch of abstract mathematics, "the intersection of a set and its complement is the empty set".
- In English: "It's a truism that prevention is better than cure."