The Only Unnatural Sex Act Is That Which One Cannot Perform

Alfred Kinsey? Richard Brinsley Sheridan? Xaviera Hollander? William Burroughs? Sigmund Freud? Anonymous?

Dear Quote Investigator: Years ago I read a statement credited to the researcher Alfred Kinsey who was famous for producing the Kinsey Reports on sexual behavior. I do not remember the exact phrasing but the expression was similar to this:

The only unnatural act is one you cannot perform.

Kinsey’s book “Sexual Behavior in the Human Male” was released in 1948, and “Sexual Behavior in the Human Female” was published in 1953. Both of these books were very controversial when they were published. I looked through them but was unable to find the quotation. Could you explore this saying?

Quote Investigator:  A precursor to this statement appeared in a satirical comedy by the prominent Irish playwright and poet Richard Brinsley Sheridan in 1779. “The Critic: or, A Tragedy Rehearsed” was first performed in London, and it included the following line in Act 2, Scene 1:

Certainly nothing is unnatural that is not physically impossible.

This statement appeared within the comedy when a character named Puff was explaining the plot of another play which contained a love match between two characters of different nationalities: 1 2

SNEER. No scandal about Queen Elizabeth, I hope?
PUFF. O Lud! no, no.—I only suppose the Governor of Tilbury Fort’s daughter to be in love with the son of the Spanish admiral.
SNEER. Oh, is that all?
DANGLE. Excellent, Efaith!—I see it at once.—But won’t this appear rather improbable?
PUFF. To be sure it will—but what the plague! a play is not to shew occurrences that happen every day, but things just so strange, that tho’ they never did, they might happen.
SNEER. Certainly nothing is unnatural, that is not physically impossible.

QI has not yet located the statement in a work written by Alfred Kinsey. The earliest evidence known to QI of a close match appeared in 1963 in an article in the Mattachine Review by Harold L. Call who was President of the Mattachine Society. The words were credited to Alfred Kinsey: 3

I suggest that the varied forms of sexual behavior are simply a part of nature. I urge others to regard them so. I remember Dr. Kinsey once said that the only unnatural sex act is that which one cannot perform. Then let’s start accepting the fact, and chuck into the rubbish can a lot of the prudish nonsense the anti-sexualists are feeding us.

Here are additional selected citations in chronological order.

Continue reading The Only Unnatural Sex Act Is That Which One Cannot Perform


  1. 1781, “The Critic Or a Tragedy Rehearsed: A Dramatic Piece in Three Acts as it is performed at the Theatre Royal in Drury Lane” by Richard Brinsley Sheridan, Quote Page 49, Printed for T. Becket, London. (Google Books full view) link
  2. Oxford Reference Online, Quick Reference: The Critic by Richard Brinsley Sheridan, Information from The Oxford Dictionary of Plays, Entry: The Critic, Oxford University Press. (Accessed on March 20, 2013)
  3. 1963 August, Mattachine Review, Volume 9, Number 8, The Hypocrisy of Sexual Morality by Harold L. Call, Start Page 4, Quote Page 12, Published by the Mattachine Society, San Francisco, California. (Reprint edition from Arno Press, New York, 1975) (Verified with scans; thanks to Stephen Goranson and Duke University library system)