8 Philosophical Puzzles and Paradoxes

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His subject areas include philosophy, law, social science, politics, political theory, and religion.</div> </a> <div data-popper-arrow></div> </div> <span class="btn btn-link editor-link p-0 qa-byline-link gtm-byline font-12 byline-contributor text-decoration-underline"> Brian Duignan</span></div> <div class="font-serif font-12 text-gray-700"> <span class="qa-fact-checked-by">Fact-checked by</span> <div class="editor-popover popover p-0"> <a class="d-block p-20 font-12" href="/editor/The-Editors-of-Encyclopaedia-Britannica/4419" > <div class="editor-title font-16 font-weight-bold">The Editors of Encyclopaedia Britannica</div> <div class="editor-description font-12 font-serif mt-5 text-black">Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree. They write new content and verify and edit content received from contributors.</div> </a> <div data-popper-arrow></div> </div> <span class="btn btn-link editor-link p-0 qa-byline-link font-12 "> The Editors of Encyclopaedia Britannica</span></div></div> </div> <article class="topic-content content"><div class="topic-paragraph font-serif md-list-intro pt-15 pb-20"><figure class="md-assembly md-feature-assembly print-false" data-type="1" data-descid="1"><div class="md-assembly-wrapper card-media " data-type="image"><a href="https://cdn.britannica.com/05/176305-131-2D85B5C6/Casino-Gambling-Slots-Neon-Slot-machine-Luck.jpg" target="_blank" class="gtm-assembly-link position-relative d-flex align-items-center justify-content-center " data-href="*0"><img src="https://cdn.britannica.com/05/176305-131-2D85B5C6/Casino-Gambling-Slots-Neon-Slot-machine-Luck.jpg?w=1000" alt="Casino. Gambling. Slots. Slot machine. Luck. Rich. Neon. Hit the Jackpot neon sign lights up casino window." data-width="900" data-height="675" loading="eager"><button class="magnifying-glass btn btn-circle position-absolute shadow btn-white top-10 right-10" aria-label="Zoom in"><em class="material-icons link-blue" data-icon="zoom_in"></em></button></a></div><figcaption class=""><div class="md-assembly-caption text-muted font-14 font-serif "><span></span></div><cite class="credit d-block mt-5">AdstockRF</cite></figcaption></figure> <p class="topic-paragraph">Plato and Aristotle both held that philosophy begins in wonder, by which they meant puzzlement or perplexity, and many philosophers after them have agreed. Ludwig Wittgenstein considered the aim of philosophy to be “to show the fly the way out of the fly bottle”—to liberate ourselves from the puzzles and paradoxes created by our own misunderstanding of language. His teacher, Bertrand Russell, remarked in a joking mood that “The point of philosophy is to start with something so simple as not to seem worth stating, and to end with something so paradoxical that no one will believe it.”</p><span class="MOD1"></span> <p class="topic-paragraph">Whether paradox is the beginning or the end of philosophy, it has certainly stimulated a great deal of philosophical thinking, and many paradoxes have served to encapsulate important philosophical problems (many others have been exposed as fallacies).</p><span class="MOD2"></span> <p class="topic-paragraph">The following list presents eight influential philosophical puzzles and paradoxes dating from ancient times to the present. Take a look and be perplexed.</p><span class="MOD3"></span> </div><ul class="md-list-order-reverse md-mendel-list" style="counter-reset: item 9"><li><h2>The liar</h2><div><figure class="md-assembly md-feature-assembly print-false" data-type="1" data-descid="1"><div class="md-assembly-wrapper card-media " data-type="image"><a href="https://cdn.britannica.com/66/167266-004-D66017A1/Epimenides.jpg" target="_blank" class="gtm-assembly-link position-relative d-flex align-items-center justify-content-center " data-href="*188562"><img src="https://cdn.britannica.com/66/167266-004-D66017A1/Epimenides.jpg?w=1000" alt="Epimenides poet and prophet of Greece." data-width="404" data-height="400" loading="eager"><button class="magnifying-glass btn btn-circle position-absolute shadow btn-white top-10 right-10" aria-label="Zoom in"><em class="material-icons link-blue" data-icon="zoom_in"></em></button></a></div><figcaption class=""><div class="md-assembly-caption text-muted font-14 font-serif "><span><a class="gtm-assembly-link md-assembly-title font-weight-bold d-inline font-sans-serif mr-5 media-overlay-link" target="_blank" href="https://cdn.britannica.com/66/167266-004-D66017A1/Epimenides.jpg" data-href="*188562">Epimenides</a></span></div><cite class="credit d-block mt-5">Promptuarii Iconum Insigniorum</cite></figcaption></figure><p class="topic-paragraph">Suppose someone tells you “I am lying.” If what she tells you is true, then she is lying, in which case what she tells you is false. On the other hand, if what she tells you is false, then she is not lying, in which case what she tells you is true. In short: if “I am lying” is true then it is false, and if it is false then it is true. The paradox arises for any sentence that says or implies of itself that it is false (the simplest example being “This sentence is false”). It is attributed to the ancient Greek seer <a href="https://www.britannica.com/biography/Epimenides" class="md-crosslink " data-show-preview="true">Epimenides</a> (fl. c. 6th century BCE), an inhabitant of Crete, who famously declared that “All Cretans are liars” (consider what follows if the declaration is true).</p><span class="MOD4"></span><p class="topic-paragraph">The <a href="https://www.britannica.com/topic/liar-paradox" class="md-crosslink " data-show-preview="true">liar paradox</a> is important in part because it creates severe difficulties for logically rigorous theories of truth; it was not adequately addressed (which is not to say solved) until the 20th century.</p><span class="MOD5"></span></div><span class="LIST-ITEM-1"></span></li><li><h2>Zeno’s paradoxes</h2><div><figure class="md-assembly md-feature-assembly print-false" data-type="1" data-descid="2"><div class="md-assembly-wrapper card-media " data-type="image"><a href="https://cdn.britannica.com/51/2351-004-224C159E/Zeno-paradox-tortoise-Achilles.jpg" target="_blank" class="gtm-assembly-link position-relative d-flex align-items-center justify-content-center " data-href="*123642"><img src="https://cdn.britannica.com/51/2351-004-224C159E/Zeno-paradox-tortoise-Achilles.jpg?w=1000" alt="Figure 1: Zeno's paradox, illustrated by Achilles racing a tortoise." data-width="553" data-height="470" loading="eager"><button class="magnifying-glass btn btn-circle position-absolute shadow btn-white top-10 right-10" aria-label="Zoom in"><em class="material-icons link-blue" data-icon="zoom_in"></em></button></a></div><figcaption class=""><div class="md-assembly-caption text-muted font-14 font-serif "><span><a class="gtm-assembly-link md-assembly-title font-weight-bold d-inline font-sans-serif mr-5 media-overlay-link" target="_blank" href="https://cdn.britannica.com/51/2351-004-224C159E/Zeno-paradox-tortoise-Achilles.jpg" data-href="*123642">Zeno's paradox</a><span>Zeno's paradox, illustrated by Achilles' racing a tortoise.</span></span></div><cite class="credit d-block mt-5">Encyclopædia Britannica, Inc.</cite></figcaption></figure><p class="topic-paragraph">In the 5th century BCE, <a href="https://www.britannica.com/biography/Zeno-of-Elea" class="md-crosslink " data-show-preview="true">Zeno of Elea</a> devised a number of paradoxes designed to show that reality is single (there is only one thing) and motionless, as his friend <a href="https://www.britannica.com/biography/Parmenides-Greek-philosopher" class="md-crosslink " data-show-preview="true">Parmenides</a> had claimed. The paradoxes take the form of arguments in which the assumption of plurality (the existence of more than one thing) or motion are shown to lead to contradictions or absurdity. Here are two of the arguments:</p><span class="MOD6"></span><p class="topic-paragraph"><em>Against plurality:</em></p><span class="MOD7"></span><p class="topic-paragraph">(A) Suppose that reality is plural. Then the number of things there are is only as many as the number of things there are (the number of things there are is neither more nor less than the number of things there are). If the number of things there are is only as many as the number of things there are, then the number of things there are is finite.</p><span class="MOD8"></span><p class="topic-paragraph">(B) Suppose that reality is plural. Then there are at least two distinct things. Two things can be distinct only if there is a third thing between them (even if it is only air). It follows that there is a third thing that is distinct from the other two. But if the third thing is distinct, then there must be a fourth thing between it and the second (or first) thing. And so on to infinity.</p><span class="MOD9"></span><p class="topic-paragraph">(C) Therefore, if reality is plural, it is finite and not finite, infinite and not infinite, a contradiction.</p><span class="MOD10"></span><p class="topic-paragraph"><em>Against motion:</em></p><span class="MOD11"></span><p class="topic-paragraph">Suppose that there is motion. Suppose in particular that Achilles and a tortoise are moving around a track in a foot race, in which the tortoise has been given a modest lead. Naturally, Achilles is running faster than the tortoise. If Achilles is at point A and the tortoise at point B, then in order to catch the tortoise Achilles will have to traverse the interval AB. But in the time it takes Achilles to arrive at point B, the tortoise will have moved on (however slowly) to point C. Then in order to catch the tortoise, Achilles will have to traverse the interval BC. But in the time it takes him to arrive at point C, the tortoise will have moved on to point D, and so on for an infinite number of intervals. It follows that Achilles can never catch the tortoise, which is absurd.</p><span class="MOD12"></span><p class="topic-paragraph"><a href="https://www.britannica.com/topic/paradoxes-of-Zeno" class="md-crosslink " data-show-preview="true">Zeno’s paradoxes</a> have posed a serious challenge to theories of space, time, and infinity for more than 2,400 years, and for many of them there is still no general agreement about how they should be solved.</p><span class="MOD13"></span></div><span class="LIST-ITEM-2"></span></li><li><h2>Sorites</h2><div><figure class="md-assembly md-feature-assembly print-false" data-type="1" data-descid="1"><div class="md-assembly-wrapper card-media " data-type="image"><a href="https://cdn.britannica.com/37/174337-050-F3A8DBD3/rice-Grains-Rice-Starch-Brown-Mixture-grain.jpg" target="_blank" class="gtm-assembly-link position-relative d-flex align-items-center justify-content-center " data-href="*188569"><img src="https://cdn.britannica.com/37/174337-050-F3A8DBD3/rice-Grains-Rice-Starch-Brown-Mixture-grain.jpg?w=1000" alt="Grains. Rice. Starch. Brown rice. Wild rice. Mixture of American long grain and wild rice." data-width="1600" data-height="1064" loading="eager"><button class="magnifying-glass btn btn-circle position-absolute shadow btn-white top-10 right-10" aria-label="Zoom in"><em class="material-icons link-blue" data-icon="zoom_in"></em></button></a></div><figcaption class=""><div class="md-assembly-caption text-muted font-14 font-serif "><span><a class="gtm-assembly-link md-assembly-title font-weight-bold d-inline font-sans-serif mr-5 media-overlay-link" target="_blank" href="https://cdn.britannica.com/37/174337-050-F3A8DBD3/rice-Grains-Rice-Starch-Brown-Mixture-grain.jpg" data-href="*188569">rice</a></span></div><cite class="credit d-block mt-5">AdstockRF</cite></figcaption></figure><p class="topic-paragraph">Also called “the heap,” this paradox arises for any predicate (e.g., “… is a heap”, “… is bald”) whose application is, for whatever reason, not precisely defined. Consider a single grain of rice, which is not a heap. Adding one grain of rice to it will not create a heap. Likewise adding one grain of rice to two grains or three grains or four grains. In general, for any number N, if N grains does not constitute a heap, then N+1 grains also does not constitute a heap. (Similarly, if N grains <em>does</em> constitute a heap, then N-1 grains also constitutes a heap.) It follows that one can never create a heap of rice from something that is not a heap of rice by adding one grain at a time. But that is absurd.</p><span class="MOD14"></span><p class="topic-paragraph">Among modern perspectives on the <a href="https://www.britannica.com/topic/sorites-problem" class="md-crosslink " data-show-preview="true">sorites paradox</a>, one holds that we simply haven’t gotten around to deciding exactly what a heap is (the “lazy solution”); another asserts that such predicates are inherently vague, so any attempt to define them precisely is wrongheaded.</p><span class="MOD15"></span></div><span class="LIST-ITEM-3"></span></li><li><h2>Buridan’s ass</h2><div><figure class="md-assembly md-feature-assembly print-false" data-type="1" data-descid="1"><div class="md-assembly-wrapper card-media " data-type="image"><a href="https://cdn.britannica.com/68/143568-050-5246474F/Donkey.jpg" target="_blank" class="gtm-assembly-link position-relative d-flex align-items-center justify-content-center " data-href="*147030"><img src="https://cdn.britannica.com/68/143568-050-5246474F/Donkey.jpg?w=1000" alt="Donkey (Equus asinus)." data-width="800" data-height="590" loading="eager"><button class="magnifying-glass btn btn-circle position-absolute shadow btn-white top-10 right-10" aria-label="Zoom in"><em class="material-icons link-blue" data-icon="zoom_in"></em></button></a></div><figcaption class=""><div class="md-assembly-caption text-muted font-14 font-serif "><span><a class="gtm-assembly-link md-assembly-title font-weight-bold d-inline font-sans-serif mr-5 media-overlay-link" target="_blank" href="https://cdn.britannica.com/68/143568-050-5246474F/Donkey.jpg" data-href="*147030">donkey</a><span>Donkey (<em>Equus asinus</em>).</span></span></div><cite class="credit d-block mt-5">© Isidor Stankov/Shutterstock.com</cite></figcaption></figure><p class="topic-paragraph">Although it bears his name, the medieval philosopher <a href="https://www.britannica.com/biography/Jean-Buridan" class="md-crosslink " data-show-preview="true">Jean Buridan</a> did not invent this paradox, which probably originated as a parody of his theory of free will, according to which human freedom consists in the ability to defer for further consideration a choice between two apparently equally good alternatives (the will is otherwise compelled to choose what appears to be the best).</p><span class="MOD16"></span><p class="topic-paragraph">Imagine a hungry donkey who is placed between two equidistant and identical bales of hay. Assume that the surrounding environments on both sides are also identical. The donkey cannot choose between the two bales and so dies of hunger, which is absurd.</p><span class="MOD17"></span><p class="topic-paragraph">The paradox was later thought to constitute a counterexample to <a href="https://www.britannica.com/topic/principle-of-sufficient-reason" class="md-crosslink " data-show-preview="true">Leibniz’s principle of sufficient reason</a>, one version of which states that there is an explanation (in the sense of a reason or cause) for every contingent event. Whether the donkey chooses one bale or the other is a contingent event, but there is apparently no reason or cause to determine the donkey’s choice. Yet the donkey will not starve. Leibniz, for what it is worth, vehemently rejected the paradox, claiming that it was unrealistic.</p><span class="MOD18"></span></div><span class="LIST-ITEM-4"></span></li><li><h2>The surprise test </h2><div><figure class="md-assembly md-feature-assembly print-false" data-type="1" data-descid="1"><div class="md-assembly-wrapper card-media " data-type="image"><a href="https://cdn.britannica.com/56/94856-050-A18B73C4/pencil-paper-fingers-counting-tools.jpg" target="_blank" class="gtm-assembly-link position-relative d-flex align-items-center justify-content-center " data-href="*188563"><img src="https://cdn.britannica.com/56/94856-050-A18B73C4/pencil-paper-fingers-counting-tools.jpg?w=1000" alt="Elementary students wearing school uniforms at school desk working on math. Boy counting fingers. Girl pencil paper" data-width="1600" data-height="1039" loading="eager"><button class="magnifying-glass btn btn-circle position-absolute shadow btn-white top-10 right-10" aria-label="Zoom in"><em class="material-icons link-blue" data-icon="zoom_in"></em></button></a></div><figcaption class=""><div class="md-assembly-caption text-muted font-14 font-serif "><span><a class="gtm-assembly-link md-assembly-title font-weight-bold d-inline font-sans-serif mr-5 media-overlay-link" target="_blank" href="https://cdn.britannica.com/56/94856-050-A18B73C4/pencil-paper-fingers-counting-tools.jpg" data-href="*188563">math test</a></span></div><cite class="credit d-block mt-5">© davidf—E+/Getty Images</cite></figcaption></figure><p class="topic-paragraph">A teacher announces to her class that there will be a surprise test sometime during the following week. The students begin to speculate about when it might occur, until one of them announces that there is no reason to worry, because a surprise test is impossible. The test cannot be given on Friday, she says, because by the end of the day on Thursday we would know that the test must be given the next day. Nor can the test be given on Thursday, she continues, because, given that we know that the test cannot be given on Friday, by the end of the day on Wednesday we would know that the test must be given the next day. And likewise for Wednesday, Tuesday, and Monday. The students spend a restful weekend not studying for the test, and they are all surprised when it is given on Wednesday. How could this happen? (There are various versions of the paradox; one of them, called <a href="https://www.britannica.com/topic/logic-puzzle#ref283053" class="md-crosslink " data-show-preview="true">the Hangman</a>, concerns a condemned prisoner who is clever but ultimately overconfident.)</p><span class="MOD19"></span><p class="topic-paragraph">The implications of the paradox are as yet unclear, and there is virtually no agreement about how it should be solved.</p><span class="MOD20"></span></div><span class="LIST-ITEM-5"></span></li><li><h2>The lottery</h2><div><figure class="md-assembly md-feature-assembly print-false" data-type="1" data-descid="1"><div class="md-assembly-wrapper card-media " data-type="image"><a href="https://cdn.britannica.com/01/158601-050-1F79555D/The-Lottery-Scene-EBEC-Shirley-Jackson-paper.jpg" target="_blank" class="gtm-assembly-link position-relative d-flex align-items-center justify-content-center " data-href="*188564"><img src="https://cdn.britannica.com/01/158601-050-1F79555D/The-Lottery-Scene-EBEC-Shirley-Jackson-paper.jpg?w=1000" alt="Scene from the EBEC film "The Lottery" by Shirley Jackson (EBEC catalog # 047757). Closeup of the paper ballot." data-width="1600" data-height="1232" loading="eager"><button class="magnifying-glass btn btn-circle position-absolute shadow btn-white top-10 right-10" aria-label="Zoom in"><em class="material-icons link-blue" data-icon="zoom_in"></em></button></a></div><figcaption class=""><div class="md-assembly-caption text-muted font-14 font-serif "><span><a class="gtm-assembly-link md-assembly-title font-weight-bold d-inline font-sans-serif mr-5 media-overlay-link" target="_blank" href="https://cdn.britannica.com/01/158601-050-1F79555D/The-Lottery-Scene-EBEC-Shirley-Jackson-paper.jpg" data-href="*188564">lottery ticket</a></span></div><cite class="credit d-block mt-5">Encyclopædia Britannica, Inc.</cite></figcaption></figure><p class="topic-paragraph">You buy a lottery ticket, for no good reason. Indeed, you know that the chance that your ticket will win is at least 10 million to one, since at least 10 million tickets have been sold, as you learn later on the evening news, before the drawing (assume that the lottery is fair and that a winning ticket exists). So you are rationally justified in believing that your ticket will lose—in fact, you’d be crazy to believe that your ticket will win. Likewise, you are justified in believing that your friend Jane’s ticket will lose, that your uncle Harvey’s ticket will lose, that your dog Ralph’s ticket will lose, that the ticket bought by the guy ahead of you in line at the convenience store will lose, and so on for each ticket bought by anyone you know or don’t know. In general, for each ticket sold in the lottery, you are justified in believing: “<em>That</em> ticket will lose.” It follows that you are justified in believing that <em>all</em> tickets will lose, or (equivalently) that no ticket will win. But, of course, you know that one ticket will win. So you’re justified in believing what you know to be false (that no ticket will win). How can that be?</p><span class="MOD21"></span><p class="topic-paragraph">The lottery constitutes an apparent counterexample to one version of a principle known as the deductive closure of justification:</p><span class="MOD22"></span><p class="topic-paragraph"><em>If one is justified in believing P and justified in believing Q, then one is justified in believing any proposition that follows deductively (necessarily) from P and Q.</em></p><span class="MOD23"></span><p class="topic-paragraph">For example, if I am justified in believing that my lottery ticket is in the envelope (because I put it there), and if I am justified in believing that the envelope is in the paper shredder (because I put it there), then I am justified in believing that my lottery ticket is in the paper shredder.</p><span class="MOD24"></span><p class="topic-paragraph">Since its introduction in the early 1960s, the lottery paradox has provoked much discussion of possible alternatives to the closure principle, as well as new theories of knowledge and belief that would retain the principle while avoiding its paradoxical consequences.</p><span class="MOD25"></span></div><span class="LIST-ITEM-6"></span></li><li><h2>Meno’s problem</h2><div><figure class="md-assembly md-feature-assembly print-false" data-type="1" data-descid="1"><div class="md-assembly-wrapper card-media " data-type="image"><a href="https://cdn.britannica.com/88/149188-050-DC34842F/Plato-portrait-bust-original-Capitoline-Museums-Rome.jpg" target="_blank" class="gtm-assembly-link position-relative d-flex align-items-center justify-content-center " data-href="*156335"><img src="https://cdn.britannica.com/88/149188-050-DC34842F/Plato-portrait-bust-original-Capitoline-Museums-Rome.jpg?w=1000" alt="Plato, marble portrait bust; from an original of the 4th century BC; in the Capitoline Museums, Rome." data-width="1371" data-height="1600" loading="eager"><button class="magnifying-glass btn btn-circle position-absolute shadow btn-white top-10 right-10" aria-label="Zoom in"><em class="material-icons link-blue" data-icon="zoom_in"></em></button></a></div><figcaption class=""><div class="md-assembly-caption text-muted font-14 font-serif "><span><a class="gtm-assembly-link md-assembly-title font-weight-bold d-inline font-sans-serif mr-5 media-overlay-link" target="_blank" href="https://cdn.britannica.com/88/149188-050-DC34842F/Plato-portrait-bust-original-Capitoline-Museums-Rome.jpg" data-href="*156335">Plato</a><span>Plato, marble portrait bust, from an original of the 4th century <em>bce</em>; in the Capitoline Museums, Rome.</span></span></div><cite class="credit d-block mt-5">© DeAgostini/SuperStock</cite></figcaption></figure><p class="topic-paragraph">This ancient paradox is named for a character in <a href="https://www.britannica.com/biography/Plato" class="md-crosslink " data-show-preview="true">Plato</a>’s eponymous dialogue. <a href="https://www.britannica.com/biography/Socrates" class="md-crosslink " data-show-preview="true">Socrates</a> and Meno are engaged in a conversation about the nature of virtue. Meno offers a series of suggestions, each of which Socrates shows to be inadequate. Socrates himself professes not to know what virtue is. How then, asks Meno, would you recognize it, if you ever encounter it? How would you see that a certain answer to the the question “What is virtue?” is correct, unless you already knew the correct answer? It seems to follow that no one ever learns anything by asking questions, which is implausible, if not absurd.</p><span class="MOD26"></span><p class="topic-paragraph">Socrates’ solution is to suggest that basic elements of knowledge, enough to recognize a correct answer, can be “recollected” from a previous life, given the right kind of encouragement. As proof he shows how a slave boy can be prompted to solve geometrical problems, though he has never had instruction in geometry.</p><span class="MOD27"></span><p class="topic-paragraph">Although the recollection theory is no longer a live option (almost no philosophers believe in reincarnation), Socrates’ assertion that knowledge is latent in each individual is now widely (though not universally) accepted, at least for some kinds of knowledge. It constitutes an answer to the modern form of Meno’s problem, which is: how do people successfully acquire certain rich systems of knowledge on the basis of little or no evidence or instruction? The paradigm case of such “learning” (there is debate about whether “learning” is the correct term) is first-language acquisition, in which very young (normal) children manage to acquire complex grammatical systems effortlessly, despite evidence that is completely inadequate and often downright misleading (the ungrammatical speech and erroneous instruction of adults). In this case, the answer, originally proposed by <a href="https://www.britannica.com/biography/Noam-Chomsky" class="md-crosslink " data-show-preview="true">Noam Chomsky</a> in the 1950s, is that the basic elements of the grammars of all human languages are innate, ultimately a genetic endowment reflecting the cognitive evolution of the human species.</p><span class="MOD28"></span></div><span class="LIST-ITEM-7"></span></li><li><h2>Moore’s puzzle</h2><div><figure class="md-assembly md-feature-assembly print-false" data-type="1" data-descid="1"><div class="md-assembly-wrapper card-media " data-type="image"><a href="https://cdn.britannica.com/78/2778-050-D9456DAA/GE-Moore-William-Orpen-detail-pencil-drawing.jpg" target="_blank" class="gtm-assembly-link position-relative d-flex align-items-center justify-content-center " data-href="*13074"><img src="https://cdn.britannica.com/78/2778-050-D9456DAA/GE-Moore-William-Orpen-detail-pencil-drawing.jpg?w=1000" alt="G.E. Moore, pencil drawing by Sir William Orpen; in the National Portrait Gallery, London" data-width="1404" data-height="1600" loading="eager"><button class="magnifying-glass btn btn-circle position-absolute shadow btn-white top-10 right-10" aria-label="Zoom in"><em class="material-icons link-blue" data-icon="zoom_in"></em></button></a></div><figcaption class=""><div class="md-assembly-caption text-muted font-14 font-serif "><span><a class="gtm-assembly-link md-assembly-title font-weight-bold d-inline font-sans-serif mr-5 media-overlay-link" target="_blank" href="https://cdn.britannica.com/78/2778-050-D9456DAA/GE-Moore-William-Orpen-detail-pencil-drawing.jpg" data-href="*13074">G.E. Moore</a><span>G.E. Moore, detail of a pencil drawing by William Orpen; in the National Portrait Gallery, London.</span></span></div><cite class="credit d-block mt-5">Courtesy of the National Portrait Gallery, London</cite></figcaption></figure><p class="topic-paragraph">Suppose you are sitting in a windowless room. It begins to rain outside. You have not heard a weather report, so you don’t know that it’s raining. So you don’t believe that it’s raining. Thus your friend McGillicuddy, who knows your situation, can say truly of you, “It’s raining, but MacIntosh doesn’t believe it is.” But if you, MacIntosh, were to say exactly the same thing to McGillicuddy—“It’s raining, but I don’t believe it is”—your friend would rightly think you’d lost your mind. Why, then, is the second sentence absurd? As <a href="https://www.britannica.com/biography/G-E-Moore" class="md-crosslink " data-show-preview="true">G.E. Moore</a> put it, “Why is it absurd for me to say something true about myself?”</p><span class="MOD29"></span><p class="topic-paragraph">The problem Moore identified turned out to be profound. It helped to stimulate <a href="https://www.britannica.com/biography/Ludwig-Wittgenstein" class="md-crosslink " data-show-preview="true">Wittgenstein</a>’s later work on the nature of knowledge and certainty, and it even helped to give birth (in the 1950s) to a new field of philosophically inspired language study, <a href="https://www.britannica.com/science/pragmatics" class="md-crosslink " data-show-preview="true">pragmatics</a>.</p><span class="MOD30"></span><p class="topic-paragraph">I’ll leave you to ponder a solution.</p><span class="MOD31"></span></div><span class="LIST-ITEM-8"></span></li></ul><span class="AM-END-OF-ARTICLE am-inline"></span></article> </div> </div> </div> <aside class="cm-rightrail d-none d-md-block ad-rail"></aside> </div> </div> </div> <div class="grid gx-0"> <div class="col"> <div class="md-loading hidden display-4 font-weight-normal"></div> <div class="text-center my-20 mb-100"> <button class="md-infinite-load-next btn btn-blue" data-value="next-page">Load More</button> </div> </div> <div class="col-md-da-320 hidden-xs"> </div> </div></div> </div> </main> <div id="md-footer"></div> <noscript><iframe src="//www.googletagmanager.com/ns.html?id=GTM-5W6NC8" height="0" width="0" style="display:none;visibility:hidden"></iframe></noscript> <script type="text/javascript" id="_informizely_script_tag"> var IzWidget = IzWidget || {}; (function (d) { var scriptElement = d.createElement('script'); scriptElement.type = 'text/javascript'; scriptElement.async = true; scriptElement.src = "https://insitez.blob.core.windows.net/site/f780f33e-a610-4ac2-af81-3eb184037547.js"; var node = d.getElementById('_informizely_script_tag'); node.parentNode.insertBefore(scriptElement, node); } )(document); </script>  <script> window.ap3c = window.ap3c || {}; var ap3c = window.ap3c; ap3c.cmd = ap3c.cmd || []; ap3c.cmd.push(function() { ap3c.init('ZO4siT4cLwnykPnzZWJtd3Byb2Q', 'https://engage.email.britannica.com/'); ap3c.track({v: 0}); }); ap3c.activity = function(act) { ap3c.act = (ap3c.act || []); ap3c.act.push(act); }; var s, t; s = document.createElement('script'); s.type = 'text/javascript'; s.src = "https://engage.email.britannica.com/app.js"; t = document.getElementsByTagName('script')[0]; t.parentNode.insertBefore(s, t); </script> <script class="marketing-page-info" type="application/json"> {"pageType":"List","templateName":null,"pageNumber":1,"pagesTotal":10,"pageId":3822,"pageLength":null,"initialLoad":true,"lastPageOfScroll":false} </script> <script class="marketing-content-info" type="application/json"> [] </script> <script src="https://cdn.britannica.com/mendel-resources/3-130/js/libs/jquery-3.5.0.min.js?v=3.130.14"></script> <script type="text/javascript" data-type="Init Mendel Code Splitting"> (function() { $.ajax({ dataType: 'script', cache: true, url: 'https://cdn.britannica.com/mendel-resources/3-130/dist/list-page.js?v=3.130.14' }); })(); </script> <script class="analytics-metadata" type="application/json"> {"leg":"A","adLeg":"A","userType":"ANONYMOUS","pageType":"List","pageSubtype":null,"articleTemplateType":null,"gisted":false,"pageNumber":1,"hasSummarizeButton":false,"hasAskButton":false} </script> <script type="text/javascript"> EBStat={accountId:-1,hostnameOverride:'webstats.eb.com',domain:'www.britannica.com', json:''}; </script> <script type="text/javascript"> ( function() { $.ajax( { dataType: 'script', cache: true, url: '//www.britannica.com/webstats/mendelstats.js?v=1' } ) .done( function() { try {writeStat(null,EBStat);} catch(err){} } ); })(); </script> <div id="bc-fixed-dialogue"></div> </body> </html>

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8 Philosophical Puzzles and Paradoxes | Britannica