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From Wikipedia, the free encyclopedia

A paradox is a statement or group of statements that leads to a contradiction or a situation which defies intuition. The term is also used for an apparent contradiction that actually expresses a non-dual truth (cf. kōan, Catuskoti). Typically, the statements in question do not really imply the contradiction, the puzzling result is not really a contradiction, or the premises themselves are not all really true or cannot all be true together. The word paradox is often used interchangeably with contradiction. It is also used to describe situations that are ironic.[citation needed]

But many paradoxes, such as Curry's paradox, do not yet have universally accepted resolutions.

Sometimes the term paradox is used for situations that are merely surprising. The birthday paradox, for instance, is unexpected but perfectly logical. The logician Willard V. O. Quine distinguishes falsidical paradoxes, which are seemingly valid, logical demonstrations of absurdities, from veridical paradoxes, such as the birthday paradox, which are seeming absurdities that are nevertheless true.[1] Paradoxes in economics tend to be the veridical type, typically counterintuitive outcomes of economic theory, such as Simpson's paradox. In literature a paradox can be any contradictory or obviously untrue statement, which resolves itself upon later inspection.


Logical paradox

Common themes in paradoxes include self-reference, the infinite regress, circular definitions, and confusion between different levels of abstraction.

Patrick Hughes outlines three laws of the paradox:[2]

  • Self reference - An example is "This statement is false", a form of the Liar paradox. The statement is referring to itself. Another example of self reference is the question of whether the barber shaves himself in the Barber paradox.
  • Contradiction - "This statement is false"—the statement cannot be false and true at the same time.
  • Vicious circularity or infinite regress - "This statement is false"—if the statement is true, then the statement is false. In which case, the statement is true, which means the statement is false... Another example of vicious circularity is the following group of statements:
          "The statement below is false."
          "The statement above is true."

Other paradoxes involve false statements or half-truths and the resulting biased assumptions.

For example, consider a situation in which a father and his son are driving down the road. The car collides with a tree and the father is killed. The boy is rushed to the nearest hospital where he is prepared for emergency surgery. On entering the surgery suite, the surgeon says, "I can't operate on this boy. He's my son."

The apparent paradox is caused by a hasty generalization; if the surgeon is the boy's father, the statement cannot be true. The paradox is resolved if it is revealed that the surgeon is a woman, the boy's mother.

Paradoxes which are not based on a hidden error generally happen at the fringes of context or language, and require extending the context or language to lose their paradoxical quality. Paradoxes that arise from apparently intelligible uses of language are often of interest to logicians and philosophers. This sentence is false is an example of the famous liar paradox: it is a sentence which cannot be consistently interpreted as true or false, because if it is known to be false then it is known that it must be true, and if it is known to be true then it is known that it must be false. Therefore, it can be concluded that it is unknowable. Russell's paradox, which shows that the notion of the set of all those sets that do not contain themselves leads to a contradiction, was instrumental in the development of modern logic and set theory.

Thought experiments can also yield interesting paradoxes. The grandfather paradox, for example, would arise if a time traveler were to kill his own grandfather before his father was conceived, thereby preventing his own birth. This paradox can be resolved by postulating that time travel leads to parallel or bifurcating universes, or that only contradiction-free timelines are stable.

W. V. Quine (1962) distinguished between three classes of paradoxes:

  • A veridical paradox produces a result that appears absurd but is demonstrated to be true nevertheless. Thus, the paradox of Frederic's birthday in The Pirates of Penzance establishes the surprising fact that a twenty-one-year-old would have had only five birthdays, if he was born on a leap day. Likewise, Arrow's impossibility theorem demonstrates difficulties in mapping voting results to the will of the people.
  • A falsidical paradox establishes a result that not only appears false but actually is false due to a fallacy in the supposed demonstration. The various invalid mathematical proofs (e.g., that 1 = 2) are classic examples, generally relying on a hidden division by zero. Another example is the inductive form of the Horse paradox, falsely generalizes from true specific statements.
  • A paradox which is in neither class may be an antinomy, which reaches a self-contradictory result by properly applying accepted ways of reasoning. For example, the Grelling–Nelson paradox points out genuine problems in our understanding of the ideas of truth and description.

A fourth kind has sometimes been described since Quine's work.

  • A paradox which is both true and false at the same time in the same sense is called a dialetheism. In Western logics it is often assumed, following Aristotle, that no dialetheia exist, but they are sometimes accepted in Eastern traditions and in paraconsistent logics. An example might be to affirm or deny the statement "John is in the room" when John is standing precisely halfway through the doorway. It is reasonable (by human thinking) to both affirm and deny it ("well, he is, but he isn't"), and it is also reasonable to say that he is neither ("he's halfway in the room, which is neither in nor out"), despite the fact that the statement is to be exclusively proven or disproven.

Paradox in literature

The paradox as a literary device has been defined as an anomalous juxtaposition of incongruous ideas for the sake of striking exposition or unorthodox insight. It functions as a method of literary analysis which involves examining apparently contradictory statements and drawing conclusions either to reconcile them or to explain their presence.[3]

Literary or rhetorical paradoxes abound in the works of Oscar Wilde and G. K. Chesterton; other literature deals with paradox of situation. Rabelais, Cervantes, Sterne, Borges, and Chesterton are all concerned with episodes and narratives designed around paradoxes. Statements such as Wilde's "I can resist anything except temptation" and Chesterton's "spies do not look like spies" are examples of rhetorical paradox. Further back, Polonius' observation in Hamlet that "though this be madness, yet there is method in't" is a memorable third.[3]

A taste for paradox is central to the philosophies of Laozi, Heraclitus, Meister Eckhart, Kierkegaard, Nietzsche, and Tom Robbins, among many others.

Moral paradox

In moral philosophy, paradox in a loose sense plays a role in ethics debates. For instance, it may be considered that an ethical admonition to "love thy neighbour" is not just in contrast with, but in contradiction to armed neighbors actively intending murder. If the hostile neighbors succeed, it is impossible to follow the dictum. On the other hand, to attack, fight back, or restrain them is also not usually considered loving. This might be better termed an ethical dilemma rather than a paradox in the strict sense. However, for this to be a true example of a moral paradox, it must be assumed that "loving" and restraint cannot co-exist. In reality, this situation occurs often, notably when parents punish children out of love.

Another example is the conflict between a moral injunction and a duty that cannot be fulfilled without violating that injunction. For example, take the situation of a parent with children who must be fed (the duty), but cannot afford to do so without stealing, which would be wrong (the injunction). Such a conflict between two maxims is normally resolved through weakening one or the other of them: the need for survival is greater than the need to abide by the law. However, as maxims are added for consideration, the questions of which to weaken in the general case and by how much pose issues related to Arrow's impossibility theorem; it may not be possible to formulate a consistent system of ethics rules with a definite order of preference in the general case, a so-called "ethical calculus".

Paradoxes in a more strict sense have been relatively neglected in philosophical discussion within ethics, as compared to their role in other philosophical fields such as logic, epistemology, metaphysics, or even the philosophy of science. Important book-length discussions appear in Derek Parfit's Reasons and Persons and in Saul Smilansky's 10 Moral Paradoxes.

See also


  1. ^ Van Orman Quine, Willard (1966). "The Ways of Paradox". The Ways of Paradox and Other Essays. Random House. p. 5. 
  2. ^ Hughes, Patrick; Brecht, George (1975). Vicious Circles and Infinity - A Panoply of Paradoxes. Garden City, New York: Doubleday. Library of Congress Catalog Card Number 74-17611. ISBN 0-385-09917-7.  . p. 1-8. 
  3. ^ a b Rescher, Nicholas (2001). Paradoxes: Their Roots, Range, and Resolution. Chicago: Open Court. ISBN 0812694368. .

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Wikisource-logo.svg "Paradox". Encyclopædia Britannica (11th ed.). 1911. 

Source material

Up to date as of January 22, 2010
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From Wikisource

A Paradox
by Richard Lovelace

Tis true the beauteous Starre
    To which I first did bow
Burnt quicker, brighter far
    Then that which leads me now;
        Which shines with more delight:
        For gazing on that light
        So long, neere lost my sight.


Through foule, we follow faire,
    For had the World one face
And Earth been bright as Ayre,
    We had knowne neither place;
        Indians smell not their Neast:
        A Swisse or Finne tastes best,
        The Spices of the East.


So from the glorious Sunne,
    Who to his height hath got,
With what delight we runne
    To some black Cave, or Grot!
        And Heav'nly Sydney you
        Twice read, had rather view
        Some odde Romance, so new.


The God that constant keepes
    Unto his Dieties,
Is poore in Joyes, and sleepes
    Imprison'd in the skies:
        This knew the wisest, who
        From Juno stole, below
        To love a Beare, or Cow.
PD-icon.svg This work published before January 1, 1923 is in the public domain worldwide because the author died at least 100 years ago.

1911 encyclopedia

Up to date as of January 14, 2010

From LoveToKnow 1911

PARADOX (Gr. irapa, beyond, contrary to, S6Ea, opinion), a proposition or statement which appears to be at variance with generally-received opinion, or which apparently is self-contradictory, absurd or untrue, but either contains a concealed truth or may on examination be proved to be true. A "paradox" has been compared with a "paralogism" (7rapa, X6 yos, reason), as that which is contrary to opinion only and not contrary to reason, but it is frequently used in the sense of that which is really absurd or untrue.

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Up to date as of January 15, 2010

Definition from Wiktionary, a free dictionary

See also paradox




  1. paradox


Simple English

's self-flowing flask fills itself in this picture, but perpetual motion machines cannot exist.]] A paradox is a sentence in logic that cannot be true but also cannot be false. Many famous problems of this kind exist.

One of most famous paradoxes is called the liar's paradox. It is the simple sentence "This sentence is a lie."

If the sentence is true, then it is a lie, as it says. But if it is a lie, how can it be true? A lie cannot also be the truth. So the sentence being true makes it a lie.

If the sentence is a lie, then it is not as it says, it is true. But that is just what the sentence says. So that makes it true. So the sentence being a lie makes it true.

This paradox is not just true in English but in any language powerful enough for a sentence to make a claim about itself. This is true of mathematics as well. Paradox can never be removed from any symbol system that makes claims about itself.

Another example is the statement that there is no cabal. Only a cabal can know if there is no cabal, so this is either a guess, or, it is a cabal trying to pretend it does not exist.

Other famous examples:

A paradox can also arise in ethics. Taking power over others is often also required to protect them, but also, one of the things being protected is their ability to do as they please, which this power interferes with. There is another article on ethical dilemma which means "a paradox arising in ethics".

Because a paradox forces us to think "out of the box", about possibilities other than true or false in logic, right or wrong in morality, it is considered very important in education. People who do not see a paradox where others do, are likely to be too certain they are right.

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