Who really said it

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

Q: Did Albert Einstein say "Two things are infinite: the universe and human stupidity; and I'm not sure about the universe"?

No. Perls printed the first half in 1947 and credited it to an unnamed "great astronomer" — not Einstein. Twenty-two years later, in 1969, he wrote "As Albert Einstein once said to me…" and, in a second book the same year, added the punchline about not being sure about the universe. The entire Einstein attribution rests on Perls' recollection of a conversation, decades after the fact.

Not Einstein — assembled by Fritz Perls between 1947 and 1969 Frederick (Fritz) Perls 1893–1970 · German-born psychiatrist, founder of Gestalt therapy

Disputed In copyright

Perls printed the first half in 1947 and credited it to an unnamed “great astronomer” — not Einstein. Twenty-two years later, in 1969, he wrote “As Albert Einstein once said to me…” and, in a second book the same year, added the punchline about not being sure about the universe. The entire Einstein attribution rests on Perls’ recollection of a conversation, decades after the fact.

Last verified 20 Jul 2026 · how we verify · spot an error?

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Disputed credit — copy with the correction

“Two things are infinite: the universe and human stupidity; and I'm not sure about the universe” Two things are infinite, as far as we know — the universe and human stupidity. —Frederick S. Perls, Ego, Hunger and Aggression (1947). Commonly misattributed to Albert Einstein.

The slide-ready mistake: crediting this to Albert Einstein. Use the credit shown above instead.

Can you use it?

Still under copyright (rights held by Frederick Perls estate / Real People Press). A short, credited quote is generally fine for talks, teaching, and internal decks; for commercial, published, or large-scale reuse, get permission.

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In context

Evoking the world of Albert Einstein — theoretical physicist. Theme: "Two things are infinite: the universe and human stupidity; and I'm not sure about the universe". Atmospheric and restrained, cinematic directional light, a muted period-appropriate palette, fine grain and texture. Compose with generous empty space for the quote and a small credit line. No lettering in the image itself.

Minimalist

Minimalist editorial slide for the quote "Two things are infinite: the universe and human stupidity; and I'm not sure about the universe". Clean background, a single muted accent color, generous negative space, subtle paper or linen texture, no literal illustration — let the words carry it. Reserve clear space for a serif quote and a small credit line. No lettering in the image itself.

Provenance

The source

First appearance: Ego, Hunger and Aggression (George Allen & Unwin, 1947), p. 111
As printed in 1947: credited to an unnamed “great astronomer”
Einstein credit added: Gestalt Therapy Verbatim (1969), p. 33
Punchline added: In and Out the Garbage Pail (1969), p. 52

Two things are infinite, as far as we know — the universe and human stupidity. Perls, 1947

The line as Perls first published it in 1947 — no Einstein, no punchline. Both were added by Perls himself twenty-two years later.

Quote Investigator — the 1947-to-1969 trace with page numbers

How we traced it

The earliest known printing is Perls’ Ego, Hunger and Aggression (1947), p. 111 — and there the line is credited not to Einstein but to an unnamed ‘great astronomer’ Quote Investigator ↗.
In Gestalt Therapy Verbatim (1969), p. 33, Perls writes ‘As Albert Einstein once said to me: “Two things are infinite: the universe and human stupidity”’ — the first time the name appears anywhere full trace ↗.
The modern form, with the closing joke, appears in Perls’ In and Out the Garbage Pail (1969), p. 52: ‘…and I am not yet completely sure about the universe.’ Snopes reaches the same conclusion — no Einstein source exists Snopes ↗.

In copyright

In copyright. All three Perls books — Ego, Hunger and Aggression (1947), Gestalt Therapy Verbatim (1969) and In and Out the Garbage Pail (1969) — remain protected, so quote a short excerpt with citation rather than reproducing passages. Note the practical trap: presenting the line as Einstein’s implies it is public domain, since Einstein’s own words have largely fallen out of copyright. It isn’t. This is not legal advice.

Fact-check

The attribution problem

This is an unusually clean case, because the same author published the line three times over twenty-two years and the attribution changed each time — all of it in print, all of it dated.

An unnamed “great astronomer” no Einstein

Perls’ first printing credits the thought to an unnamed astronomer. If Einstein had said it to him, this was the moment to say so trace ↗.

“As Albert Einstein once said to me” credit appears 22 years later

The Einstein attribution surfaces for the first time in Gestalt Therapy Verbatim, framed as personal recollection. No corroboration exists from Einstein’s side, and no such meeting is documented.

Added by Perls later embellishment

‘And I am not yet completely sure about the universe’ appears only in Perls’ second 1969 book — the funniest part of the quotation is the part furthest from any Einstein source Snopes ↗.

Not Einstein. First published by Fritz Perls in 1947 crediting an unnamed astronomer, re-credited to Einstein by Perls in 1969, and completed with its punchline the same year full trace ↗.

Context

Why it resonates

The joke works because of who is supposedly telling it. Coming from the man who measured the universe, ‘I’m not sure about the universe’ is a devastating throwaway; coming from anyone else it is merely a good line.

That is the mechanism behind a great many invented quotations: the wit is real, but it needs borrowed authority to land, and the borrowing is what makes it spread.

In 1947 it was an unnamed astronomer. Only in 1969 did it become Einstein.

The three printings

Perls, Ego, Hunger and Aggression (1947), p. 111: ‘Two things are infinite, as far as we know — the universe and human stupidity’ — credited to an unnamed great astronomer.

Perls, Gestalt Therapy Verbatim (1969), p. 33: ‘As Albert Einstein once said to me…’

Perls, In and Out the Garbage Pail (1969), p. 52: ‘…and I am not yet completely sure about the universe.’

Open question: whether the line also appears in the earlier 1942 South African edition of Ego, Hunger and Aggression has not been verified.

Explore

Filed under

More provenance-checked quotes on the same theme, each with its reuse status.

Doubt Knowledge

Go further

Dig deeper

Trusted places to keep pulling the thread — primary archives, fact-checks, and scholarship. We show how we used each one before you leave.

Two Things Are Infinite: The Universe and Human Stupidityquoteinvestigator.com

The full chain with page numbers, and the conclusion that the saying’s accuracy ‘depends on the mutable memory of Perls.’

Did Einstein say the universe and human stupidity are infinite?snopes.com

Independent fact-check reaching the same finding: no Einstein source, origin with Perls.

Albert Einstein — Wikiquote (misattributed)en.wikiquote.org

Carries the line only in the misattributed section, not among Einstein’s sourced statements.

Popularly credited author

Why it gets pinned on Einstein

Albert Einstein

1879–1955 · theoretical physicist

Albert Einstein (1879–1955) is the default signature for any remark that sounds both clever and world-weary. The joke needs a speaker with the standing to pronounce on the size of the universe, and Einstein is the obvious candidate — which is presumably why Perls reached for his name in 1969, having managed without it in 1947. There is no record of the two men ever discussing the subject.

For writers & researchers

Cite this

Primary source — Chicago

Perls, Frederick S. Ego, Hunger and Aggression: A Revision of Freud’s Theory and Method. London: George Allen & Unwin, 1947, p. 111.

MLA (9th ed.)

Perls, Frederick S. Ego, Hunger and Aggression: A Revision of Freud’s Theory and Method. George Allen & Unwin, 1947, p. 111.

APA (7th ed.)

Perls, F. S. (1947). Ego, hunger and aggression: A revision of Freud’s theory and method (p. 111). George Allen & Unwin.

This verification page

Quotle.info. “Who really said ‘Two things are infinite: the universe and human stupidity’?” Last verified 20 Jul 2026. https://quotle.info/who-said/two-things-are-infinite-the-universe-and-human-stupidity