Two things are infinite: the universe and human stupidity; and I’m not sure about the universe.

No source in Einstein’s writings has been found, and Perls is the only known source who reports hearing it from him. The earliest known printing is in Frederick S. Perls, Ego, Hunger and Aggression: A Revision of Freud’s Theory and Method (London: George Allen and Unwin, 1947), chapter ‘Hunger Instinct’, p. 111: ‘it is not surprising to learn that a great astronomer said: “Two things are infinite, as far as we know—the universe and human stupidity.” To-day we know that this statement is not quite correct. Einstein has proved that the universe is limited.’ (A first edition appeared in Durban in 1942; Quote Investigator did not check it, and neither could this run.) The 1969 Vintage reprint keeps ‘a great astronomer’. In the same year Perls named Einstein twice: in Gestalt Therapy Verbatim (Real People Press, 1969, p. 33): ‘As Albert Einstein once said to me: “Two things are infinite: the universe and human stupidity.”’; and in his memoir In and Out the Garbage Pail (Real People Press, 1969, unnumbered page counted as 52 by Quote Investigator), after an afternoon he spent with Einstein: ‘I still love to quote a statement of his: “Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe.”’ Quote Investigator (2010, revised 2025) answers ‘Probably not’ and concludes that ‘the accuracy of the saying apparently depends on the mutable memory of Perls’; Alice Calaprice’s The Ultimate Quotable Einstein (Princeton University Press, 2011) lists it, as a variant of ‘The difference between genius and stupidity is that genius has its limits’, under ‘Probably Not by Einstein’; Wikiquote lists it under Disputed. The ‘I’m not sure about the former/universe’ wordings of today are later popular forms of Perls’s 1969 tagline; Wikiquote’s earliest for ‘Only two things are infinite … I’m not sure about the former’ is Technocracy Digest (1988, p. 76), not checked here. The joke about boundless human stupidity is much older and French: Flaubert wrote to Maupassant on 19 February 1880 ‘La terre a des limites, mais la bêtise humaine est infinie’ (printed in Maupassant’s Des vers, 1880), and Larousse’s Grand dictionnaire universel du XIXe siècle (vol. 2, c. 1865–66, article ‘Bêtise’) credits to Alexandre Dumas: ‘Une chose qui m’humilie profondément est de voir que le génie humain a des limites, quand la bêtise humaine n’en a pas.’ Searched: archive.org full text for ‘universe and human stupidity’, ‘two things are infinite’, ‘not yet completely sure about the universe’, ‘as far as we know—the universe and human stupidity’ and ‘Albert Einstein once said to me’ (earliest hit Perls 1947; nothing earlier found); the DLI scan of the 1947 London edition of Ego, Hunger and Aggression read in context; Calaprice 2011 searched inside on archive.org.

Shared as a quip of Einstein’s about human folly, on quotation sites, posters, school yearbooks and in books of humorous quotations; on Goodreads it is among the most liked quotes of all (149,278 likes in October 2026), tagged ‘attributed-no-source’. No letter, essay, interview or speech by Einstein has been found to contain it (Calaprice 2011 lists it under “Probably Not by Einstein”). Every early trace leads to one man, the Gestalt therapist Frederick (Fritz) Perls, who printed the saying three times, in three forms, crediting it first to ‘a great astronomer’ and only later to Einstein.

Human stupidity has no limit, and the joke’s twist is that the universe, the stock example of the infinite, may be finite while stupidity is not.

Quoted as a physicist’s verdict, as if Einstein had weighed the size of the universe against human folly. In its first known printing, in 1947, Perls gave it to an unnamed astronomer and then said Einstein’s work contradicted it, since ‘Einstein has proved that the universe is limited’. The tagline that doubts the universe’s infinity, which makes it sound like Einstein, appears only in 1969.

Not found in Einstein’s writings. If you use it, say ‘attributed to Einstein’ or credit it as Fritz Perls reported it (Gestalt Therapy Verbatim, 1969); Perls’s first version (1947) gave it to an unnamed astronomer.

• The form on posters and social mediaTwo things are infinite: the universe and human stupidity; and I’m not sure about the universe. The Goodreads form, credited to Albert Einstein (Goodreads popular quotes #4, 149,278 likes, tagged ‘attributed-no-source’, October 2026). Calaprice (2011) prints the same wording as a variant under ‘Probably Not by Einstein’. Where it was seen
• The form on posters and social mediaOnly two things are infinite, the universe and human stupidity, and I’m not sure about the former. The other common form, credited to Einstein in joke and quotation books from the 1990s on (here Best Jokes & Other Humor from the Internet, 1997); Wikiquote’s earliest is Technocracy Digest (1988), not checked here. Where it was seen
• ShortenedTwo things are infinite: the universe and human stupidity. Perls’s own short form, which he says Einstein ‘once said to me’, in Gestalt Therapy Verbatim (1969), p. 33. Where it was seen
• Another public-domain translationZwei Dinge sind unendlich: das Universum und die menschliche Dummheit. Aber beim Universum bin ich mir nicht ganz sicher. The German form in circulation, as Wikiquote gives it; Wikiquote’s earliest German version is in Hans Askenasy, Sind wir alle Nazis? (1979), p. 153, not checked here. Where it was seen

• Alexandre Dumas (as credited by Larousse): The same joke a century before Perls, that human genius has its limits and human stupidity none: ‘Une chose qui m’humilie profondément est de voir que le génie humain a des limites, quand la bêtise humaine n’en a pas.’
• Gustave Flaubert, 1880: In a letter to Guy de Maupassant, ‘the earth has limits, but human stupidity is infinite’: ‘La terre a des limites, mais la bêtise humaine est infinie!’

• I have nothing to declare except my genius. (not found) Oscar Wilde
• I can resist everything except temptation. Oscar Wilde
• No man needs a vacation so much as the man who has just had one. (misattributed) Elbert Hubbard
• Times are bad. Children no longer obey their parents, and everyone is writing a book. (not found) Marcus Tullius Cicero
• I had the radio on. Marilyn Monroe

• quoteinvestigator.com/2010/05/04/universe-einstein (Quote Investigator, ‘Two Things Are Infinite: The Universe and Human Stupidity’, 4 May 2010, updated 2 January 2025)
• en.wikiquote.org/wiki/Albert_Einstein#Disputed
• archive.org/details/dli.scoerat.14012egohungerandaggression (Perls, Ego, Hunger and Aggression, London 1947, p. 111; scan read in context)
• archive.org/details/egohungeraggress0000perl (the 1969 Vintage reprint, still ‘a great astronomer’; full-text search)
• archive.org/details/gestalttherapyve00perl (Perls, Gestalt Therapy Verbatim, 1969, p. 33; full-text search)
• archive.org/details/inoutgarbagepail00perlrich (Perls, In and Out the Garbage Pail, 1969; full-text search)
• archive.org/details/ultimatequotable0000eins (Alice Calaprice, The Ultimate Quotable Einstein, 2011: ‘Probably Not by Einstein’; full-text search)
• archive.org/details/desvers00maupgoog (Maupassant, Des vers, 1880: Flaubert’s letter of 19 February 1880)
• archive.org/details/LarousGrdictionnXIX02bnf (Larousse, Grand dictionnaire universel du XIXe siècle, vol. 2, ‘Bêtise’)

“Two things are infinite: the universe and human stupidity; and I’m not sure about the universe.” Attributed to Albert Einstein. No. It is not in Einstein’s works, and who first wrote it is not known. Quotogeny, https://quotogeny.com/q/two-things-are-infinite/ (checked 21 October 2026).

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