Card Paradox

	Card Paradox The card paradox is a variant of the liar paradox constructed by Philip Jourdain. It is also known as the postcard paradox, Jourdain paradox or Jourdain's paradox. The paradox Suppose there is a card with statements printed on both sides: Trying to assign a truth value to either of them leads to a paradox. # If the first statement is true, then so is the second. But if the second statement is true, then the first statement is false. It follows that if the first statement is true, then the first statement is false. # If the first statement is false, then the second is false, too. But if the second statement is false, then the first statement is true. It follows that if the first statement is false, then the first statement is true. The same mechanism applies to the second statement. Neither of the sentences employs (direct) self-reference, instead this is a case of circular reference A circular reference is a series of references where the last object references the first ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Liar Paradox In philosophy and logic, the classical liar paradox or liar's paradox or antinomy of the liar is the statement of a liar that they are lying: for instance, declaring that "I am lying". If the liar is indeed lying, then the liar is telling the truth, which means the liar just lied. In "this sentence is a lie" the paradox is strengthened in order to make it amenable to more rigorous logical analysis. It is still generally called the "liar paradox" although abstraction is made precisely from the liar making the statement. Trying to assign to this statement, the strengthened liar, a classical binary truth value leads to a contradiction. If "this sentence is false" is true, then it is false, but the sentence states that it is false, and if it is false, then it must be true, and so on. History The Epimenides paradox (circa 600 BC) has been suggested as an example of the liar paradox, but they are not logically equivalent. The semi-mythical seer Epimenides, a Cretan, reportedly stated t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Philip Jourdain Philip Edward Bertrand Jourdain (16 October 1879 – 1 October 1919) was a British logician and follower of Bertrand Russell. Background He was born in Ashbourne in Derbyshire* one of a large family belonging to Emily Clay and his father Francis Jourdain (who was the vicar at Ashbourne). His sister Eleanor Jourdain was an English academic and author. Another sister, Margaret (1876–1951), was an authority on the history of fine English home-furnishings, and the life-long companion of the novelist Ivy Compton-Burnett. Mathematics and logic Jourdain was partly disabled by Friedreich's ataxia. He corresponded with Georg Cantor and Gottlob Frege, and took a close interest in the paradoxes related to Russell's paradox, formulating the card paradox version of the liar paradox.History and Root of the Principle of Conservation of Energy* 1915: Ernst MacThe Science of Mechanics* 1915: Georg Cantorbr>Contributions to the Foundation of the Theory of Transfinite Numbers References * Ivor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Paradox A paradox is a logically self-contradictory statement or a statement that runs contrary to one's expectation. It is a statement that, despite apparently valid reasoning from true premises, leads to a seemingly self-contradictory or a logically unacceptable conclusion. A paradox usually involves contradictory-yet-interrelated elements that exist simultaneously and persist over time. They result in "persistent contradiction between interdependent elements" leading to a lasting "unity of opposites". In logic, many paradoxes exist that are known to be invalid arguments, yet are nevertheless valuable in promoting critical thinking, while other paradoxes have revealed errors in definitions that were assumed to be rigorous, and have caused axioms of mathematics and logic to be re-examined. One example is Russell's paradox, which questions whether a "list of all lists that do not contain themselves" would include itself, and showed that attempts to found set theory on the identification ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]