Certitude is not the test of certainty. We have been cock-sure of many things that were not so. is a quote of American Supreme Court Justice Oliver Wendell Holmes, Jr. (1841 - 1935). The quote is found in an article written by Justice Holmes in 1918 for the "Harvard Law Review" v. 32, page 40. The quote is also found in the book "Statistically Speaking, a Dictionary of Quotations" by Carl Gaither and Alma Cavazos-Gaither.