Some evidence for Henry Buckle (1821-1862) as the source: see p.33 quotation

There are many published incidents of this as an anonymous proverb since at least 1948, and as a statement of Eleanor Roosevelt since at least 1992, but without any citation of an original source. It is also often attributed to Admiral Hyman G. Rickover but, though Rickover quoted this, he did not claim to be the author of it; in "The World of the Uneducated" in The Saturday Evening Post (28 November 1959), he prefaces it with "As the unknown sage puts it..."

Great minds discuss ideas, average minds discuss events, and little minds discuss people. | In this form it was quoted as an anonymous epigram in A Guide to Effective Public Speaking (1953) by Lawrence Henry Mouat | New York times Saturday review of books and art, 1931: ...Wanted, the correct quotation and origin of this expression: Great minds discuss ideas, average minds discuss events, small minds discuss people... | Several other variants or derivatives of the expression exist, but none provide a definite author | Great minds discuss ideas, mediocre minds discuss events, small minds discuss personalities. | Great minds discuss ideas Average minds discuss events Small minds discuss people | Small minds discuss things Average minds discuss people Great minds discuss ideas | ...Be less curious about people and more curious about ideas. (Marie Curie, undated (died 1934), as quoted in Living Adventures in Science by Henry and Dana Lee Thomas, 1972) | ...Some professor of psychology who has been eavesdropping for years makes the statement that "The best minds discuss ideas; the second in ranking talk about things; while the third group, or the least in mentality, gossip about people"… (Hardware age, Volume 123, 1929) | ...He now reports that, "the best minds discuss ideas; the second ranking talks about things; while the third and lowest mentality – starved for ideas – gossips about people." (Printers' Ink, Volume 139, Issue 2, 1927, p. 87) | ...It has been said long ago that there were three classes of people in the world, and while they are subject to variation, for elemental consideration they are useful. The first is that large class of people who talk about people; the next class are those who talk about things; and the third class are those who discuss ideas... (H. J. Derbyshire, "Origin of mental species", 1919) | ...Mrs. Conklin points out certain bad conversational habits and suggests good ones, quoting Buckle's classic classification of talkers into