WIST

Logic is an organized way of going wrong with confidence.

Charles F. Kettering (1876-1958) American inventor, engineer, researcher, businessman
“Kettering’s Law,” from address before American Society of Mechanical Engineers (c. 1944)

Quoted in Heinlein, The Number of the Beast (1980).

Alternately quoted:

• "Beware logic. Logic is an organized way to go wrong -- with confidence."
• Logic is an organized way to go wrong with confidence. We should all know by now that a logical course is not always the right one."

Sometimes referred to "Kettering's Observation."

Cited in Food Industries magazine, vol. 16 (1944), referring to the speech being "recent" (the magazine is also referred to as Food Engineering).

This site previously incorrectly attributed the quote to Iris Murdoch.  That attribution seems to have been duplicated at some other sites, but was an error.  I have also found citations to L. Walter Lundell and Karl Popper.

Another "Kettering's Law" that is referenced is: "Parts left out cost nothing, require no maintenance, and do not fail."