paradox

Etymology

From Middle French paradoxe, from Latin paradoxum, from Ancient Greek παράδοξος (parádoxos, “unexpected, strange”).

noun

1. An apparently self-contradictory statement, which can only be true if it is false, and vice versa.
   "This sentence is false" is a paradox.
   According to one version of an ancient paradox, an Athenian is supposed to say "I am a liar." It is then argued that if the statement is true, then he is telling the truth, and is therefore not a liar […] 1962, Abraham Wolf, Textbook of Logic, page 255
2. A counterintuitive conclusion or outcome.
   It is an interesting paradox that drinking a lot of water can often make you feel thirsty.
   The most fundamental paradox is that if we're never to use force, we must be prepared to use it and to use it successfully. May 21 1983, Ronald Reagan, Presidential Radio Address
3. A claim that two apparently contradictory ideas are true.
   Not having a fashion is a fashion; that's a paradox.
   How quaint the ways of Paradox! / At common sense she gaily mocks! / Though counting in the usual way years twenty-one I've been alive, / Yet reck'ning by my natal day, / Yet reck'ning by my natal day, / I am a little boy of five! 1879, W. S. Gilbert, “The Pirates of Penzance”, in The Complete Plays of Gilbert and Sullivan, published 1941
4. A thing involving contradictory yet interrelated elements that exist simultaneously and persist over time.
5. A person or thing having contradictory properties.
   He is a paradox; you would not expect him in that political party.
   You are a paradox of bitch and angel. 1999, Virginia Henley, A Year and a Day, page 315
6. An unanswerable question or difficult puzzle, particularly one which leads to a deeper truth.
   And only by dismantling our preconceptions of age can we be free to understand the paradox: How young are the old? 1994, James Joseph Pirkl, Transgenerational Design, page 3
7. (obsolete) A statement which is difficult to believe, or which goes against general belief.
   Ay, truly; for the power of beauty will sooner / transform honesty from what it is to a bawd than the / force of honesty can translate beauty into his / likeness: this was sometime a paradox, but now the / time gives it proof. 1594, William Shakespeare, The Tragedy of Hamlet, Prince of Denmark, Act III
   they contended to make that Maxim, that there is no faith to be held with Infidels, a meere and absurd Paradox …. 1615, Ralph Hamor, A True Discourse of the Present State of Virginia, Richmond, published 1957, page 3
8. (uncountable) The use of counterintuitive or contradictory statements (paradoxes) in speech or writing.
   The need for paradox is no doubt rooted deep in the very nature of the use we make of language. 1906, Richard Holt Hutton, Brief Literary Criticisms, page 40
9. (uncountable, philosophy) A state in which one is logically compelled to contradict oneself.
   Thus, like modern disputants, they aimed either to confute the respondent or to land him in paradox. 1866, Edward Poste, Aristotle on Fallacies, Or, The Sophistici Elenchi, translation of original by Aristotle, page 43
10. (countable, uncountable, psychotherapy) The practice of giving instructions that are opposed to the therapist's actual intent, with the intention that the client will disobey or be unable to obey.
    Defiance-based paradox is employed so that the family will actively oppose and deliberately sabotage the prescription. 1988, Martin Lakin, Ethical Issues in the Psychotherapies, page 103