In Theory There Is No Difference Between Theory and Practice, While In Practice There Is

Yogi Berra? Albert Einstein? Richard Feynman? Benjamin Brewster? Charles F. Kettering? Walter J. Savitch? Jan L. A. van de Snepscheut? Dave Jeske? Chuck Reid?

Dear Quote Investigator: The following popular adage balances unsteadily between brilliance and absurdity:

In theory, theory and practice are the same. In practice, they are not.

This notion has been attributed to many people including famous baseball player Yogi Berra, scientific genius Albert Einstein, and prominent physicist Richard P. Feynman. What do you think?

Quote Investigator: There is no substantive reason to credit Berra, Einstein, or Feynman. The expression was coined before Einstein had reached his third birthday and before the other two were born.

The earliest strong match located by QI appeared in “The Yale Literary Magazine” of February 1882 which was written and edited by students. Benjamin Brewster who was a member of the class of 1882 wrote about an argument he had engaged in with a philosophical friend about theory versus practice. His companion accused him of committing a vulgar error. Emphasis added to excerpts by QI: 1

I heard no more, for I was lost in self-reproach that I had been the victim of “vulgar error.” But afterwards, a kind of haunting doubt came over me. What does his lucid explanation amount to but this, that in theory there is no difference between theory and practice, while in practice there is?

Brewster was humorously summarizing the position of his friendly opponent, and QI believes that the saying should be credited to Brewster.

Below are additional selected citations in chronological order.

The Quote Investigator website has an article exploring a distinct but related saying: That works very well in practice, but how does it work in theory?

In 1961 a collection of speeches by Charles F. Kettering was published under the title “Prophet of Progress”. Kettering was the influential head of research at General Motors Corporation for many years. During an address he made a thematically matching point: 2

There is no warfare between theory and practice. But theory without practice isn’t much use. A friend of mine once said that there is no difference between theory and practice. There is one difference. Practice won’t let you forget anything or leave anything out. In theory, problems are easily solved because you can leave something out.

In 1984 a computer textbook titled “Pascal: An Introduction to the Art and Science of Programming” by Walter J. Savitch provided an anonymous ascription: 3

In theory, there is no difference between theory and practice; but in practice, there is.
Remark overheard at a computer science conference.

In 1987 a journalist writing in “Computerworld” presented a similar observation: 4

In theory, there is no difference between theory and practice, but in practice, as most programmers know, there is practically no similarity between theory and practice. This maxim applies to C compilers for IBM mainframes.

In 1996 a message posted to the Usenet discussion system credited Nobel-Prize-winning scientist Richard Feynman: 5

In theory, there is no difference between theory and practice. In practice, there is. –Richard P. Feynman

In 1997 a confused individual posted an inquiry to the alt.quotations newsgroup of the Usenet discussion system. Seven different authorship candidates including Yogi Berra were listed for the expression under examination: 6

Often I read this lovely quote: “In theory there is no difference between theory and practice. In practice there is.” I have searched through the WWW and found it frequently, as stated above or slightly modified.

It is said to be due to Yogi Berra, J. Templeman, Dave Jeske, Chuck Reid, Jan L.A. van de Snepscheut, Flash Gordon, Joe Golab, … no wonder that many just state the author as “anonymous”.

But to get this solved once and for all, I call upon the wisdom of alt.quotations: Where is the quote from?

A Usenet message from 1998 presented an anonymous variant: 7

Seen on a button or bumper sticker:
There is no difference between theory and practice in theory, but there is often a great deal of difference between theory and practice in practice.

In May 2000 a newspaper in Sioux City, Iowa credited Yogi Berra: 8

TODAY’S QUOTE: “In theory there is no difference between theory and practice. In practice there is.” – Yogi Berra

In July 2000 a Usenet message in the newsgroup fa.linux.hams credited luminary Albert Einstein: 9

“In theory there is no difference between theory and practice. In practice there is.”
Albert Einstein

In conclusion, Benjamin Brewster should receive credit for the saying based on the 1882 citation. Charles F. Kettering crafted a variant that was published in 1961. The version in the 1984 textbook may have been created independently, but the attribution was anonymous. Other attributions are unsupported.

Image Notes: Graphic of theory and practice from geralt on Pixabay. Cover of “The Yale Literary Magazine” from 1882.

(Great thanks to Steve Hoffenberg, Maria Konnikova, Julia Galef, Peter Sokolowski, Barry Schachter, Casciano Pasqualino, Shaun Partlow, Shantanu Sapru, and Daniel Gackle whose inquiries led QI to formulate this question and perform this exploration. Special thanks to previous researchers, e.g., Barry Popik who pointed to the 1984 textbook by Walter J. Savitch as a first citation. Also, thanks to the researchers at Snopes who pointed to the same textbook. In addition, thanks to the volunteer Wikiquote editors who pointed to Jan L. A. van de Snepscheut who was born in the 1950s.)


  1. 1882 February, The Yale Literary Magazine, Conducted by the Students of Yale College, Volume 47, Number 5, Portfolio: Theory and Practice by Benjamin Brewster, Quote Page 202, New Haven, Connecticut. (Google Books Full View) link
  2. 1961, Prophet of Progress: Selections from the Speeches of Charles F. Kettering, Edited by T. A. Boyd, Speech Title: Lap-Welding Students to Life, Quote Page 34 and 35, E. P. Dutton and Company, New York. (Verified with scans)
  3. 1984 Copyright, Pascal: An Introduction to the Art and Science of Programming by Walter J. Savitch (University of California, San Diego), Section: Summary of Problem Solving and Programming Techniques, (Freestanding quotation), Quote Page 366, The Benjamin/Cummings Publishing Company, Menlo Park, California. (Verified with scans)
  4. 1987 May 4, Computerworld, In Depth: C invades final frontier: IBM 370 environments by Dan Woods, Start Page 59, Quote Page 60, Column 4, Publisher: IDG Communications, Computerworld Editorial Office, Framingham, Massachusetts. (Internet Archive link
  5. 1996 December 23, Usenet discussion message, Newsgroup: alt.polyamory, From: Stef Jones, Subject: Re: Disrupting relationships (Was: Re: “Stealing” people), (Google Groups Search; Accessed April 14, 2018) link
  6. 1997 October 23, Usenet discussion message, Newsgroups: alt.quotations, From: Joern Lodahl, Organization: Departments of Mathematical Sciences, Subject: who said: In theory there is no difference…? (Google Groups Search; Accessed April 13, 2018) link
  7. 1998 March 14, Usenet discussion message, Newsgroup: alt.motd, From: Culture Time: 20 PAST MIDNIGHT, Subject: Culture Time: 20 PAST MIDNIGHT. (Google Groups Search; Accessed April 13, 2018) link
  8. 2000 May 12, The Sioux City Journal, Today’s Quote, Quote Page A8, Column 4, Sioux City, Iowa. (Newspapers_com)
  9. 2000 July 26, Usenet discussion message, Newsgroup: fa.linux.hams, From: Eamon Skelton, Subject: Re: NEWQPSK tests, (Google Groups Search; Accessed April 14, 2018) link