Inliterary criticism and rhetoric, a tautology is a statement that repeats an idea, using near-synonymous morphemes, words or phrases, effectively "saying the same thing twice".[1][2] Tautology and pleonasm are not consistently differentiated in literature.[3] Like pleonasm, tautology is often considered a fault of style when unintentional. Intentional repetition may emphasize a thought or help the listener or reader understand a point.[4] Sometimes logical tautologies like "Boys will be boys" are conflated with language tautologies, but a language tautology is not inherently true, while a logical tautology always is.[4]
The word was coined in Koine Greek from ταὐτός ('the same') plus λόγος ('word' or 'idea'), and transmitted through 3rd-century Latin tautologia and French tautologie. It first appeared in English in the 16th century. The use of the term logical tautology was introduced in English by Wittgenstein in 1919, perhaps following Auguste Comte's usage in 1835.[5]
Abbreviations whose last word is often redundantly repeated.[6][7]
Intentional repetition of meaning intends to amplify or emphasize a particular, usually significant fact about what is being discussed. For example, a gift is, by definition, free of charge; using the phrase "free gift" might emphasize that there are no hidden conditions or fine print (such as the expectation of money or reciprocation) or that the gift is being given by volition.
This is related to the rhetorical deviceofhendiadys, where one concept is expressed through the use of two descriptive words or phrases: for example, using "goblets and gold" to mean wealth, or "this day and age" to refer to the present time. Superficially, these expressions may seem tautological, but they are stylistically sound because the repeated meaning is just a way to emphasize the same idea.
The use of tautologies, however, is usually unintentional. For example, the phrases "mental telepathy", "planned conspiracies", and "small dwarfs" imply that there are such things as physical telepathy, spontaneous conspiracies, and giant dwarfs, which are oxymorons.[8]
Parallelism is not tautology, but rather a particular stylistic device. Much Old Testament poetry is based on parallelism: the same thing said twice, but in slightly different ways (Fowler describes this as pleonasm).[1] However, modern biblical study emphasizes that there are subtle distinctions and developments between the two lines, such that they are usually not truly the "same thing". Parallelism can be found wherever there is poetry in the Bible: Psalms, the Books of the Prophets, and in other areas as well.
