oxymoron

/ɒksɪˈmɔːɹɒn/

/ɑksɪˈmɔɹɑn/

First attested in the 17th century, noun use of 5th century Latin oxymōrum (adjective), neut. nom. form of oxymōrus (adjective), from Ancient Greek ὀξύμωρος (oxúmōros), compound of ὀξύς (oxús, “sharp, keen, pointed”) (English oxy-, as in oxygen) + μωρός (mōrós, “dull, stupid, foolish”) (English moron (“stupid person”)). Literally "sharp-dull", "keen-stupid", or "pointed-foolish" – itself an oxymoron, hence autological; compare sophomore (literally “wise fool”), influenced by similar analysis. The compound form ὀξύμωρον (oxúmōron) is not found in the extant Ancient Greek sources.

In Oxymoron jarring phrases join
And terms opposed in harmony combine.

[1835, L[arret] Langley, A Manual of the Figures of Rhetoric, […], Doncaster: Printed by C. White, Baxter-Gate, →OCLC, page 35:

For Theodor Adorno and his colleagues at the Frankfurt School who coined the term, "culture industry" was an oxymoron, intended to set up a critical contrast between the exploitative, repetitive mode of industrial mass production under capitalism and the associations of transformative power and aesthetico-moral transcendence that the concept of culture carried in the 1940s, when it still meant "high" culture.

1996, John Sinclair, “Culture and Trade: Some Theoretical and Practical Considerations”, in Emile G. McAnany, Kenton T. Wilkinson, editors, Mass Media and Free Trade: NAFTA and the Cultural Industries, University of Texas Press:

(rhetoric) A figure of speech in which two words or phrases with opposing meanings are used together intentionally for effect.


antinomy

en-noun

antinomy (countable and uncountable, plural antinomies)

LL-Q1860 (eng)-I learned some phrases-antinomy.wav

Learned borrowing from Latin antinomia + English -y (suffix forming abstract nouns denoting a condition, quality, or state); antinomia is derived from Ancient Greek ἀντινομία (antinomía), from ἀντι- (anti-, prefix meaning ‘against’) (ultimately from Proto-Indo-European *h₂ent- (“face; forehead; front”)) + νόμος (nómos, “custom, usage; law, ordinance”) + -ῐ́ᾱ (-ĭ́ā, suffix forming feminine abstract nouns), with νόμος (nómos) derived from νέμω (némō, “to deal out, dispense, distribute”) (from Proto-Indo-European *nem- (“to distribute; to give; to take”)) + -ος (-os, suffix forming nouns indicating actions or their results). The English word may be analysed as anti- (prefix meaning ‘against; opposite of’) + -nomy (suffix indicating a system of laws, rules, or knowledge about a body of a particular field).

confix

This introduces the antinomy that has followed us through the whole study. The solution of this antinomy is found in making the Not-me, which interrupts self-consciousness, really reflect self-consciousness, by manifesting the nature of the I—in other words, by making it conform to the ideal of the soul.

1884, Charles Carroll Everett, Fichte’s Science of Knowledge: A Critical Exposition, page 12:

Of the work that has been done on the liar antinomy, possibly the most profound and certainly the most influential has been that of Tarski

1991, Vann McGee, Truth, Vagueness, & Paradox: An Essay on the Logic of Truth, page 67:

(by extension) Any contradiction or paradox.

(specifically, epistemology, logic) In the thought of the German philosopher Immanuel Kant (1724–1804): an apparent contradiction between valid conclusions; a paradox.

التضاد

(epistemology, logic) apparent contradiction between valid conclusions


paradox

en-noun

paradox (countable and uncountable, plural paradoxes)

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

{{t|af|paradoks}

apparent contradiction which is nonetheless true

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, →ISBN, page 315:

A person or thing having contradictory properties.

矛盾的人

person or thing with contradictory properties


Coined by American author Joseph Heller in 1961 in his novel Catch-22, in which the main character feigns madness in order to avoid dangerous combat missions, but his desire to avoid them is taken to prove his sanity.

coin

For us it’s been a real Catch-22: when we have the time to take a vacation, we don’t have enough money, and when we have enough money, we don’t have the time.

Herein lies my personal “Catch 22”; the choice between three hours sleep and some discomfort or six hours sleep and real pain. Usually I choose the lesser evil of insomnia because in addition to the pain at 6am, I am incapacitated by the hangover from the sedative.

1988, E[dward] J[ames] Moran Campbell, Not Always on the Level, [London]: British Medical Journal, →ISBN, page 194:

(idiomatic) A difficult situation from which there is no escape because it involves mutually conflicting or dependent conditions.


heterological

From Ancient Greek ἕτερος (héteros, “different”) + λόγος (lógos, “word”), by surface analysis, heterology + -ical.

der

The normally situated non-transplanted gonads have the best chance of being able to absorb these substances, for which reason heterological (perhaps also homological) gonads, transplanted on normal organisms, can not get enough of these substances and therefore perish.

Growth indices from density and extension of the zones of emigration in explants of rat bone-marrow on addition of various heterological tissue as against the controls.

1983, Franz Schmid, Cell Therapy: A New Dimension of Medicine, page 106:

(biology, of biomolecules, tissues, or body parts) Not of shared ancestral origin.

tissues; or body parts; tissues; or body parts


Olbers' paradox

From Heinrich Wilhelm Matthäus Olbers, German astronomer.

(astronomy) The observation that the night sky is mostly dark, yet, in a boundless universe of stars, every line of sight from the eye must eventually intercept the surface of a star.

Heinrich Wilhelm Matthäus Olbers
Olbers' paradox


paradoxical

en-adj

paradoxical (comparative more paradoxical, superlative most paradoxical)

more paradoxical (comparative)
most paradoxical (superlative)

/ˌpæɹəˈdɒksɪkəl/

/ˌpɛɹəˈdɑːksɪkəl/

It is the ambiguity of language only which can make this proposition appear either doubtful or paradoxical. When properly explained and understood, it is almost self-evident.

1776, Adam Smith, An Inquiry into the Nature and Causes of the Wealth of Nations, book II, ch 2:

It sounds paradoxical, but I am inclined to think that the weakness and insanity of the curate warned me, braced me, and kept me a sane man.

1898, H. G. Wells, The War of the Worlds, Book 2, ch 4:

By some paradoxical evolution rancour and intolerance have been established in the vanguard of primitive Christianity. Mrs. Spoker, in common with many of the stricter disciples of righteousness, was as inclement in demeanour as she was cadaverous in aspect.

1921, Ben Travers, chapter 4, in A Cuckoo in the Nest, Garden City, N.Y.: Doubleday, Page & Company, published 1925, →OCLC:

It was tightly fitted with a cap of the same substance, and bore engraved figurings of an evidently decorative and possibly symbolic nature - conventional designs which seemed to follow a peculiarly alien, paradoxical, and doubtfully describable system of geometry.

1933, H. P. Lovecraft, Hazel Heald, Out of the Aeons:

The new civilizationism is a paradoxical combination of “identitarian” Christianity, secularism, philo-Semitism, Islamophobia, and even some elements of liberalism such as support for gender equality and gay rights.

2017 December 6, Rogers Brubaker, “The New Language of European Populism”, in brubaker.scholar.ss.ucla.edu, page 2:


clock paradox

(relativity) The phenomenon in which two observers who start together with identical clocks, follow different timelines, and then rejoin can have different elapsed times on their clocks, especially if one travels at a relativistic speed.


twin paradox

twin paradoxes (plural)
twins paradox (alternative)

From the thought experiment conducted by Albert Einstein, in which one of a pair of twins sets off in a spaceship on a trip at high speed, and due to the effects of relativity, his effective clock ticks slower than the twin who remains at home, not encountering relativistic effects, so that when the spacetraveller twin returns home to compare clocks, the spacetraveller will have experienced less elapsed time than the homebody, thus having aged less than the homebody twin and being younger.


chicken-or-egg question

en-noun

chicken-or-egg question (plural chicken-or-egg questions)

chicken-or-egg questions (plural)
chicken or egg question (alternative)
chicken-and-egg question (alternative)
chicken and egg question (alternative)
chicken-and-egg problem (alternative)
hen and egg question (alternative)
hen-and-egg question (alternative)
hen or egg question (alternative)
hen-or-egg question (alternative)
hen-and-egg problem (alternative)

(logic, philosophy) A supposed paradox concerning whether chickens or chicken eggs existed first.

(by extension) A question to decide which of two interdependent things happened first.

مُعْضِلَة الدَجَاجَةِ وَالبَيْضَةِ

a question to decide which of two interdependent things happened first


Russell's paradox

Named after English mathematician, logician and philosopher Bertrand Russell.

named-after

One concludes that there must be something fishy about the Axiom of Comprehension, and, over time, the replacement of the Axiom of Comprehension by the Schema of Separation was seen to resolve Russell's paradox. Indeed, one cannot apply the Schema of Separation as in Russell's paradox unless one knows in advance that the collection of all sets is itself a set.

1999, R. C. Penner, Discrete Mathematics: Proof Techniques and Mathematical Structures, World Scientific, page 109:

The well-known theorem of Tarski that truth of sentences in any reasonably expressive language L cannot be defined in the language L itself is proved by a diagonalization argument similar to the argument involved in Russell's paradox.[…]It is usual to think that Russell's paradox excludes "large" sets like the universe, but this is actually not the case. An alternate solution to Russell's paradox (and other paradoxes) was proposed by Quine (1937) in his system "New Foundations" (NF): comprehension restricted to stratified formulae.

2001, M. Randall Holmes, “Tarski's Theorem and NFU”, in C. Anthony Anderson, Michael Zelëny, editors, Logic, Meaning and Computation: Essays in Memory of Alonzo Church, Springer (Kluwer Academic), page 469:

2013, Greg Frost-Arnold, Carnap, Tarski, and Quine at Harvard: Conversations on Logic, Mathematics, and Science, Carus Publishing Company (Open Court), page 43,
Roughly, the idea is that Russell's paradox reveals that certain logics suffer serious problems, and therefore these logics should be avoided. […] Here again, Quine asserts that the real lesson of Russell's paradox is that we should give up quantifying over abstracta.

(set theory) The paradox that a set defined to contain all sets which do not contain themselves can neither consistently contain itself nor not contain itself.

Axiom schema of specification
Russell's paradox


Fermi paradox

Named after physicist Enrico Fermi (1901–1954).

Fermi argued that the fact that aliens don't seem to be hanging out with us here on Earth (the tabloid stories aside) strongly contradicts the assumed existence of intelligent life elsewhere in our galaxy, a problem that came to be known as the Fermi Paradox.

2006, Kevin W. Plaxco, Michael Gross, Astrobiology: A Brief Introduction, →ISBN, page 246:

(exobiology) The seeming contradiction, serving as a challenge to believers in the existence of advanced lifeforms throughout the universe, that there is no scientific evidence that extraterrestrial civilizations have tried to visit or communicate with Earth.


grandfather paradox

en-noun

grandfather paradox (plural grandfather paradoxes)

From the paradox proposed by the French author René Barjavel in 1944 in his book Le Voyageur Imprudent, translated into English as "Future Times Three"; in its original form the paradox of one person going back to the past and killing their biological grandfather before the latter fathered the traveler's father, thus preventing the time traveler from ever being conceived in the first place.

The paradox of time travel in which inconsistencies emerge through changing the past.

Future Times Three
René Barjavel
grandfather paradox


Buridan's ass

After the fourteenth-century French philosopher Jean Buridan, whose philosophy of moral determinism it satirizes.

Buridan is best-known to philosophers for the example of "Buridan's Ass," starving to death between two equidistant and equally tempting bales of hay, [...]

1985, Jean Buridan, Peter King, Jean Buridan's Logic, Springer, →ISBN, page 3:

They remain like Buridan's Ass, in a kind of frozen indecisiveness, between total freedom and total regulation.

2003 August 31, Tony Dermody <tdermody@iol.NODAMNJUNK.ie>, “Re: A Few Questions”, in alt.atheism.moderated (Usenet), message-ID <2lpcvpdh3zwc$.1mk81eq1qmfo3$.dlg@40tude.net>:

Did you refuse to choose between saving your son sentenced to death penalty and saving your son sentenced to slavery for life? Is that not an indication that you find no difference between them, and are frozen, as Buridan's ass, into an inability to choose between them, and have instead chosen to starve morally, rather than make such a choice?

2003 September 6, Euro <euro82@excite.com>, “PV's small arrangements with truth”, in alt.activism.death-penalty (Usenet), message-ID <4f3f4d56.0309061154.3fea3b3a@posting.google.com>:

The worst case for productivity is probably when two _perfectly equivalent_ ways exist. Buridan's ass notoriously starved to death in just such a worst-case situation; groups of programmers may not go quite as far, but are sure to waste lots of time & energy deciding.

2003 October 11, Alex Martelli <aleaxit@yahoo.com>, “Re: Python syntax in Lisp and Scheme”, in comp.lang.python, comp.lang.lisp, comp.lang.scheme (Usenet), message-ID <gGWhb.200390$hE5.6777507@news1.tin.it>:

The hypothetical donkey who is placed precisely midway between two sources of food or water.

The hypothetical donkey in the context of certainly dying of hunger or thirst by being unable to choose between the two equidistant options.

Since either haystack is better than starvation, and since neither haystack is known to be worse than the other, Buridan's ass has a good reason to choose either. Suppose it chooses haystack A, rejecting haystack B as well as starvation.

1995, Ross Harrison, World, mind, and ethics: essays on the ethical philosophy of Bernard Williams, illustrated edition, Cambridge University Press, →ISBN, page 23:

This Narrator is like the famous or infamous Buridan's ass, protagonist of a problem or example that, in one form or another, can be found in philosophical discourse from Aristotle to Schpenhauer.

2000, Kathryn L. Lynch, Chaucer's philosophical visions, illustrated edition, Boydell & Brewer Ltd, →ISBN, page 90:

The ass's commitment to a seeming demand or rationality has damaged his health. Maybe we — and Buridan's ass — should often resist requiring a discriminating reason for rational action.

2009, Peter Cave, This sentence is false: an introduction to philosophical paradoxes, Continuum International Publishing Group, →ISBN, page 9:

The hypothetical donkey, as a typical character of a number of philosophical paradoxes involving equally valuable incentives to action, and the nature of the possible choices and outcomes.


Buridan's ass

Buridan's ass (countable and uncountable, plural Buridan's asses)

Buridan's asses (plural)
Buridan's Ass (alternative)

The National Peace Council was, I will not say a Buridan's Ass, but a kind of eunuch organisation, unable to take a decision one way or another.

1972, Sir George Edward Gordon Catlin, For God's sake, go!: an autobiography:

(countable, chiefly derogatory) A person or organization who does not make a choice.

Not that they are Buridan's ass; they just do not believe in categorical decisions.

1972, The Statesman, volume 22, page 76:

You are Buridan's ass, in your immoral refusal to head toward one or the other of what you claim are irresistible allures of 'human rights.'

2003 August 11, A Planet Visitor <abcxyz@zbqytr.ykq>, “Re: Where is Europe....Where is France”, in alt.activism.death-penalty (Usenet), message-ID <tc3ejvkr2qekfefd2fp90esv07vu8fqtcl@4ax.com>:

You know the opinion you hold. You just will not divulge it... in cowardly fear of him turning on you. And not divulging it will not in the slightest keep him from turning on you whenever he feels like it. Please do not tell me you are Buridan's ass, and have no opinion about this.

2005 May 6, Doctor Make U. Feelgood <nappynospam@eatthlink.net>, “Re: Yom Hashoah”, in alt.activism.death-penalty (Usenet), message-ID <LIidncWpaYTpj-HfRVn-tQ@giganews.com>:

(uncountable, chiefly derogatory) Collectively, people who do not make a choice.


Berry paradox

Bertrand Russell, the first to discuss the paradox in print, attributed it to G. G. Berry (1867–1928), a junior librarian at Oxford's Bodleian library, who had suggested the more limited paradox arising from the expression "the first undefinable ordinal".

A particular self-referential paradox relating to the number of words in a descriptive phrase.


Richard's paradox

First described by the French mathematician Jules Richard in 1905.

The paradox where, given the observation that certain English phrases unambiguously define real numbers while others do not, there is an infinitely long list of English phrases that unambiguously define real numbers, yet (using a similar technique to Cantor's diagonal argument) it is possible to generate another such phrase not in the list.


Grelling-Nelson paradox

Formulated in 1908 by Kurt Grelling and Leonard Nelson.

A semantic paradox of self-reference, where, supposing that "autological" means "self-describing" and "heterological" means "not self-describing", then "heterological" itself cannot be meaningfully classified as either of the two.


barber paradox

A paradox of self-reference, where, supposing that every man either shaves himself or is shaved by the barber, and the barber shaves all and only the men who do not shave themselves, then it is impossible to determine who shaves the barber.


liar paradox

liar paradoxes (plural)
liar's paradox (alternative)

Graham Priest has argued the liar paradox is a true dialetheia.

(philosophy, logic) A paradox involving statements such as "this sentence is false", or "the following statement is true: the previous statement is false", which cannot be meaningfully regarded as either true or false.


Newcomb's paradox

Created by William Newcomb of the University of California.

A thought experiment involving a game between two players, one of whom purports to be able to predict the future. The first player has to try to maximize winnings by choosing one of two boxes of money; however, the amount won also depends on whether a prediction made about the choice by the other player proves to be true.


hyperloop

Musk began developing another transportation project in 2012, something he calls the Hyperloop.

2012, Scott Griffiths, Eric Elfman, Beyond Genius, →ISBN, page 210:

Whatever – the result is the same: they usually jump in front of the nearest hyperloop shuttle.

2014, Gideon Defoe, Elite Dangerous: Docking is Difficult, →ISBN:

There is a small handful of groups working in earnest on making Elon Musk's dream of a hyperloop a reality, but none are so high profile as Hyperloop Technologies.

2015 September 16, Casey Newton, “Hyperloop Technologies has a CEO — and plans to open its test track next year”, in The Verge:

Then in 2013 we all find out who Elon Musk is, the Tesla, Space X^([sic]) and hyperloop guy.

2015, Landry Hunt, Jeremiah Nichols, The System, →ISBN:

Will the fate of the hyperloop concept be different from the maglev and be introduced quickly and successfully on the market?

2015, S. Van Themsche, The Advent of Unmanned Electric Vehicles, →ISBN, page 369:

Musk also features in the other piece of bad news for the tech enthusiasts - the effective collapse of the hyperloop, as the technical limitations of the idea have become all too apparent. [...] Firstly, in February, Virgin announced it was abandoning plans to create a passenger-carrying hyperloop system and made the 100 staff working on the project redundant. Then, early in November, it was revealed that Musk's test tube for hyperloop has been dismantled with no explanation, with the site now being used as a car park.

2022 November 30, Christian Wolmar, “The railway endures as driverless cars hit the buffers...”, in RAIL, number 971, page 57:

A theoretical high-speed transportation system, proposed by Elon Musk, in which pressurized capsules ride on an air cushion driven by linear induction motors and air compressors through reduced-pressure tubes.

If Hal finds a value of x such that fun(x), Hal sends a signal to Dave (perhaps a light-beam). Dave carries a receiving device with him, which stores a variable, xFound, initialised to a default value of 0; this receiver sets xFound to 1 on (and only on) receipt of a signal from Hal. Once Dave reaches point r, Hal's entire infinite history lies in Dave's past, and any signal that Hal might have sent to Dave will have arrived. So from Dave's perspective, by point r, Hal has completed a hyperloop.

2009, Klaus Ambos-Spies, Benedikt Löwe, Wolfgang Merkle, Mathematical Theory and Computational Practice, →ISBN, page 70:

(computing) A control structure in which a loop repeats until either a stopping condition is met or all possible values of the looping index have been checked.

At this point, the hyperloop breaks in. A holographic virtual image is presented to an optical observer. Where is the observer of the image formed from Gij? Presumably, it is the physicist. But the physicist is himself an image projected from the same source. We still have a self-viewing system, and a no-exit loop.

1984, Alex Comfort, Reality and Empathy, →ISBN:

Even more jaw-rattling is the problem of what is being called the "hyperloop." The Helmholtzian view of mind — that it is exhaustively explainable in terms of the electrochemical activity of brain — is a solid article of faith for most well-dressed scientists, for all practical purposes, even if they also have religious opinions which include immortal souls, divine sparks, and the like: those are strictly idiosyncratic contraband and belong in a different box. But in modern physics, our definitions of matter-energy and space-time require the insertion of mind as a primitive component: the brain consists of the particulars it observes.

1985, Christopher Chapple, Religious experience and scientific paradigms, page 6:

His concern in this paper is with the relations of Bohm's implicate to a "hyperloop" (the "observer paradox "), which Comfort variously describes as "matter thinking itself' (1981: 363), as the process "by which the brain generates 4-space by object formation from the plenum.

1989, Glendon A. Schubert, Evolutionary politics, page 317:

When the subgraph is a hyperloop, the associated equation is a relation involving no variables: in the unfrustrated case, it is just a trivial identity; in the frustrated case, it is a configuration-independent characteristic of the instance which could eventually determine a priori unsatisfiability.

2002, Institute of Physics (Great Britain), Journal of Physics: Mathematical and general, page 7670:

(quantum mechanics) A quantum mechanical paradox resulting from the observer being a product of the observations that it makes.


ship of Theseus

A thought experiment that raises the question of whether an object that has had all of its components replaced (specifically, a ship whose parts have all been replaced) remains fundamentally the same object.


strange loop

A situation where, by moving only upwards or downwards through a hierarchical system, one finds oneself back where one started. These loops often involve self-reference and paradox.


paradox of fiction

paradox of fiction (plural paradoxes of fiction)

(philosophy) The paradox that (i) people have emotional responses to fictitious events, and (ii) one must believe that something truly exists in order to be emotionally moved by it, but (iii) nobody who considers an event to be fictitious can also believe it to be real.


Galileo's paradox

Named after the scientist Galileo, though he did not originate the concept.

(set theory) A demonstration of a surprising property of infinite sets. Some positive integers are squares while others are not; therefore, all the numbers, including both squares and non-squares, must be more numerous than just the squares; yet for every square there is exactly one positive number that is its square root, and for every number there is exactly one square; hence, there cannot be more of one than of the other.


d'Alembert's paradox

Observed in 1752 by French mathematician Jean le Rond d'Alembert.

(fluid dynamics) The contradiction that, for incompressible and inviscid potential flow, the drag force is zero on a body moving with constant velocity relative to the fluid.


Curry's paradox

A paradox that occurs in naive set theory or naive logics, and allows the derivation of an arbitrary sentence from a self-referring sentence and some apparently innocuous logical deduction rules.


Löb's paradox

Named after Martin Hugo Löb, due to its relationship to Löb's theorem.


paradox of thrift

paradox of thrift (plural paradoxes of thrift)

The worse things get, meanwhile, the greater the tendency even for those who still feel secure in their jobs to hoard their cash for fear of what lies around the corner. This is the so-called paradox of thrift: that in a recession, people instinctively try to save their money instead of spending it, and thus inadvertently make things worse.

2020 April 9, Gaby Hinsliff, “We used to moan about normal life, now our fear is we'll never get it back”, in The Guardian:

(economics) A paradox of economics, in which an increase in autonomous saving leads to a decrease in aggregate demand and thus a decrease in gross output which will in turn lower total saving.


gentle murder paradox

A paradox of deontic logic, whereby the plausible statements (i) if you murder, you ought to murder gently, (ii) you do commit murder, and (iii) to murder gently you must murder imply the less plausible statement (iv) you ought to murder.


Hawking's paradox

(physics) The black hole information paradox.


paradox of saving

paradox of saving (plural paradoxes of saving)

paradox of thrift
paradox of thrift#English


Thomson's lamp

The idea was devised in 1954 by British philosopher James F. Thomson.

(philosophy) A hypothetical lamp in a philosophical paradox. The lamp is repeatedly turned on and off by means of a switch; at the end of this time period, regarded as the sum of an infinite series of intervals, it seems paradoxically that the lamp cannot be either on or off.


unexpected hanging paradox

Coordinate term: surprise test paradox

A paradox about a person's expectations about the timing of a future event which they are told will occur at an unexpected time. It is based on the idea that a prisoner, told that he will be hanged on a day unknown to him, concludes that "I cannot be hanged on Friday because if I haven't been hanged by the end of Thursday then it would no longer be a surprise", and so on backwards through the week.


observer's paradox

observer's paradox (plural observer's paradoxes)

The situation in which a phenomenon being observed for study is unintentionally influenced by the presence of the observer.


sorites paradox

sorites paradox (plural sorites paradoxes)

(logic) A paradox arising from vague predicates and repeatedly applying a small difference. For example, removing one grain from a heap of sand still leaves a heap, yet removing enough grains will eventually not leave a heap.


Buridan's bridge

(philosophy) A self-referential paradox involving a proposition pronounced about an event that might or might not happen in the future. Socrates wishes to cross a bridge guarded by Plato, who says that if the next proposition Socrates utters is true, Socrates will be permitted to cross, but otherwise he will be thrown into the water. Socrates replies, "You will throw me into the water." Plato is then in a paradoxical situation regarding how to treat Socrates.


Zeno's paradox

Zeno's paradox (plural Zeno's paradoxes)

(philosophy) Any of a set of philosophical problems generally thought to have been devised by the Greek philosopher Zeno of Elea (c. 490–430 BC) to support Parmenides' doctrine that, contrary to the evidence of one's senses, the belief in plurality and change is mistaken, and in particular that motion is nothing but an illusion.


Grim Reaper paradox

A philosophical problem related to Benardete's paradox, but involving countably many Grim Reapers, each of which will kill the person in question at a certain time (if still alive), taking a certain period of time to do it.


Ehrenfest paradox

(physics) A relativistic paradox concerning the concept of Born rigidity within special relativity, where an ideally rigid cylinder that is made to rotate about its axis of symmetry. The radius R as seen in the laboratory frame is always perpendicular to its motion and should therefore be equal to its value R₀ when stationary. However, the circumference should appear Lorentz-contracted to a smaller value than at rest. This leads to the contradiction that R = R₀ and R < R₀.


interesting number paradox

the interesting number paradox (canonical)

(mathematics) A humorous paradox arising from the attempt to classify every natural number as either "interesting" or "uninteresting". If there exists a non-empty set of uninteresting natural numbers, there must be a smallest uninteresting number, but this number is paradoxically interesting because it is the smallest uninteresting number.


infinite hotel paradox

(set theory) A thought experiment illustrating a counterintuitive property of infinite sets, showing that a fully occupied hotel with infinitely many rooms can still accommodate any number of additional guests.


surprise test paradox

unexpected hanging paradox
unexpected hanging paradox

A variation of the unexpected hanging paradox in which the future event of unknown date is not a hanging but an academic test.


potato paradox

potato paradox (plural potato paradoxes)

(economics): In reference to the 1845 Irish famine, when potatoes became expensive. It has been argued that poorer families, who habitually ate more potatoes, ended up having to consume even more of them, since the higher prices made it even harder to afford any other goods.

(economics) The paradoxical nature of Giffen goods, where people consume more as the price rises.


Sagan's paradox

The apparent contradiction between the high probability of the existence of extraterrestrial beings and the lack of observed evidence for such beings.


tea leaf paradox

(fluid dynamics) The phenomenon whereby tea leaves in a cup of tea migrate to the center and bottom of the cup after being stirred (due to friction towards the bottom), rather than being forced to the edges, as would be expected in a spiral centrifuge.