An absurdity is a thing that is extremely unreasonable, so as to be foolish or not taken seriously, or the state of being so. "Absurd" is an adjective used to describe an absurdity, e.g., "this encyclopedia article is absurd". It derives from the Latin absurdum meaning "out of tune", hence irrational. The Latin surdus means "deaf", implying stupidity. Absurdity is contrasted with seriousness in reasoning. In general usage, absurdity may be synonymous with ridiculousness and nonsense. In specialized usage, absurdity is related to extremes in bad reasoning or pointlessness in reasoning; ridiculousness is related to extremes of incongruous juxtaposition, laughter, and ridicule; and nonsense is related to a lack of meaningfulness. Absurdism is a concept in philosophy related to the notion of absurdity.
Absurdity has been used throughout western history regarding foolishness and extremely poor reasoning to form belief.
In Aristophanes' 5th century BC comedy The Wasps, his protagonist Philocleon learned the "absurdities" of Aesop's Fables, considered to be unreasonable fantasy, and not true.
Plato often used "absurdity" to describe very poor reasoning, or the conclusion from adopting a position that is false and reasoning to a false conclusion, called an "absurdity" (argument by reductio ad absurdum). Plato describes himself as not using absurd argumentation against himself in Parmenides. In Gorgias, Plato refers to an "inevitable absurdity" as the outcome of reasoning from a false assumption.
Aristotle rectified an irrational absurdity in reasoning with empiricism using likelihood, "once the irrational has been introduced and an air of likelihood imparted to it, we must accept it in spite of the absurdity. He claimed that absurdity in reasoning being veiled by charming language in poetry, "As it is, the absurdity is veiled by the poetic charm with which the poet invests it… But in the Epic poem the absurdity passes unnoticed."