John Maynard Keynes? Milton Friedman? A. Gary Shilling? Albert J. Hettinger, Jr.? Apocryphal?
Dear Quote Investigator: Forbes magazine has a fascinating searchable database called “Thoughts On The Business of Life” that contains “more than 10,000 quotes.” The following saying interests me, but the database doesn’t appear to include citations so I am not sure if it is accurate [MKFQ]:
There is nothing so disastrous as a rational investment policy in an irrational world.
— John Maynard Keynes
Can you find out when and where Keynes said this?
Quote Investigator: The earliest evidence QI has located for this saying is dated 1963. It appeared in the book “A Monetary History of the United States 1867-1960” by Milton Friedman and Anna Jacobson Schwartz, but the words were not written by Friedman or Schwartz. Near the end of the volume a commentary by Albert J. Hettinger, Jr. was appended and the following passage was included [AHMK]:
And Lord Keynes, here a “decision maker,” told the 1931 annual meeting of the investment trust of which he was chairman: “I have reluctantly reached the conclusion that nothing is more suicidal than a rational investment policy in an irrational world” (quoted from memory, without verification of exact phraseology).
So Hettinger in 1963 presented a quotation that he attributed to Keynes speaking in 1931. But Hettinger explicitly disclaimed knowledge of the precise wording used by Keynes. Later writers used a different phrasing that replaced “more suicidal than” with “so disastrous as” to yield the most common modern version of the saying.
Keynes died in 1946. Here are additional selected citations in chronological order.