Quote Origin: Sunlight Is the Best Disinfectant

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Louis Brandeis? Ralph Waldo Emerson? Robert Walter? Anonymous?

Question for Quote Investigator: There is a family of sayings about the effectiveness of light for the destruction of noxious infectious agents. This family also includes metaphorical instances in which corrupt behavior is revealed and prevented via publicity. Here are some examples:

  • Sunlight is the best disinfectant.
  • Sunshine is the best disinfectant.
  • The best moral disinfectant is publicity.

Would you please explore this topic?

Reply from Quote Investigator: In 1860 the well-known transcendentalist philosopher Ralph Waldo Emerson published a collection of essays on “The Conduct of Life” which included a piece titled “Worship”. Emerson employed an analogy equating the protective illumination provided by gas-light and the protective information provided by publicity. Boldface added to excerpts by QI:1

As gas-light is found to be the best nocturnal police, so the universe protects itself by pitiless publicity.

In 1879 the journal “The Laws of Health” edited by Robert Walter published a short article without a byline about “Disinfectants” which included the following excerpt:2

Sunlight is the best disinfectant. Malaria, for instance, which is one of the most difficult things to contend against, is dissipated when the sun shines, and exerts its pernicious influence at night.

The above statement was non-metaphorical. Many years later in 1913 lawyer Louis Brandeis penned a metaphorical instance that has become popular. The fame of Brandeis grew when he joined the Supreme Court of the United States in 1916. See further below for details of the 1913 citation.

Here are additional selected citations in chronological order.

In 1886 a newspaper in Garrett, Indiana printed the non-metaphorical saying:3

Sunlight is one of the best disinfectants. The microbes that cause disease do not flourish in strong sunshine. It has also the advantage of being cheap.

In 1889 a newspaper in Marion, Kansas printed a version of the non-metaphorical saying with the word “sunshine” instead of “sunlight”:4

Don’t be afraid of sunshine. It is the best disinfectant and will keep the doctor at a distance.

In 1898 the “Buffalo Daily Times” referred to “The New York Sun” newspaper while using the metaphorical phrase “the great disinfectant of publicity”:5

The great value of the Sun’s service lies in showing now effective would be the publication by the Government of the names of all pensioners within the districts where they are known. It would subject the list to the great disinfectant of publicity, which would tend powerfully to purge it of corruption.

In 1906 a newspaper in Great Falls, Montana employed an analogy that compared the power of sunlight and publicity:6

Turn on the light and let us have a glimpse of the secret things done in the dark places in Washington. Sunlight is the great germicide and disinfectant, and publicity is healthful to the morals of government. Meantime, there is no cause for pessimism.

In 1907 a newspaper in Abilene, Kansas printed a statement listing different types of disinfectants:7

Once in awhile a public document has a live statement in it. The state board of health bulletin has this on the front page: “The best natural disinfectant, sunshine; the best germ disinfectant, formaldehyde; the best physical disinfectant, soap; the best moral disinfectant, publicity.”

In 1913 “Harper’s Weekly” published “What Publicity Can Do” by Louis D. Brandeis which began with the following words:8

Publicity is justly commended as a remedy for social and industrial diseases. Sunlight is said to be the best of disinfectants; electric light the most efficient policeman. And publicity has already played an important part in the struggle against the Money Trust.

In 1914 Brandeis published a collection of articles under the title “Other People’s Money: And How the Bankers Use It”. The book included the essay “What Publicity Can Do”; hence, the quotation above achieved further distribution.9

In 2012 “The Dictionary of Modern Proverbs” included an entry for the metaphorical saying with a citation pointing to the 1913 essay by Louis Brandeis.10

In conclusion, the non-metaphorical saying “Sunlight is the best disinfectant” was circulating by 1879 when it appeared in a journal edited by Robert Walter. The metaphorical version of the saying which references publicity evolved over time. The phrase “the great disinfectant of publicity” appeared by 1898. Louis Brandeis wrote a popular passage containing the phrase “Sunlight is said to be the best of disinfectants” in 1913.

Image Notes: Painting of “Woman in an Orchard, Spring Sunshine in a Field, Eragny” by Camille Pissarro circa 1887. Image has been resized and cropped.

Acknowledgement: Great thanks to anonymous YouTube content creator whose inquiry led QI to formulate this question and perform this exploration. Thanks also “The Yale Book of Quotations” by Fred R. Shapiro which listed the quotations by Ralph Waldo Emerson and Louis D. Brandeis.

Update History: On July 28, 2024 the format of the bibliographical notes was updated.

  1. 1860, The Conduct of Life by Ralph Waldo Emerson, Chapter 6: Worship, Start Page 175, Quote Page 197, Smith, Elder and Company, London. (Google Books Full View) link ↩︎
  2. 1879 January, The Laws of Health, Disinfectants, Quote Page 70, Column 3, Published by Robert Walter of Wernersville near Reading, Pennsylvania. (HathiTrust Full View) link ↩︎
  3. 1886 May 6, The Garrett Weekly Clipper, Sunshine, Quote Page 4, Column 5, Garrett, Indiana. (Newspapers_com) ↩︎
  4. 1889 June 1, The Rural Kansan, Household Hints, Quote Page 6, Column 4, Marion, Kansas. (Newspapers_com) ↩︎
  5. 1898 January 11, Buffalo Daily Times, What Might Be Done (From the New York Journal), Quote Page 4, Column 4, Buffalo, New York. (Newspapers_com) ↩︎
  6. 1906 January 17, Great Falls Daily Tribune, The Chase of the Grafter, Quote Page 2, Column 1, Great Falls, Montana. (Newspapers_com) ↩︎
  7. 1907 January 4, Abilene Daily Reflector, (Filler item), Quote Page 2, Column 1, Abilene, Kansas. (Newspapers_com) ↩︎
  8. 1913 December 20, Harper’s Weekly, Volume 58, Number 2974, What Publicity Can Do by Louis D. Brandeis, Start Page 10, Quote Page 10, The McClure Publications, New York. (Google Books Full View) link ↩︎
  9. 1914, Other People’s Money: And How the Bankers Use It by Louis D. Brandeis, Chapter 5: What Publicity Can Do, Quote Page 92, Frederick A. Stokes Company, New York. (Google Books Full View) link ↩︎
  10. 2012, The Dictionary of Modern Proverbs, Compiled by Charles Clay Doyle, Wolfgang Mieder, and Fred R. Shapiro, Quote Page 246, Yale University Press, New Haven. (Verified with hardcopy) ↩︎