A pessimist looks at his glass and says it is half empty; an optimist looks at it and says it is half full.

Josiah Stamp
Josiah Stamp (1880-1941) English industrialist, economist, statistician, banker
Comment (1935)

There is substantial evidence that Stamp used this now-cliched phrase, or variations of it, on multiple spoken occasions in 1935, the earliest references I could find.
  • The Railway Service Journal (later Transport Salaried Staff Journal) mentions 1935 after-dinner remarks by Stamp: "After dinner, Sir Josiah Stamp defined an optimist as 'the man who looks at his glass and says it is half full,' and the pessimist as 'the man who looks at it and says it is half empty.'" [Source]

  • Similarly, the Bristol Chamber of Commerce Journal mentions a 1935 speech: "A pessimist is a man who looks at the glass and describes it as half empty, and an optimist is a man who describes it as half full. It is all a question of the point of view." [Source]

  • A New York Times article (12 Nov 1935) includes "I came recently upon a graphic distinction drawn by Sir Josiah Stamp between an optimist and a pessimist," followed by the phrasing noted at the top. [Source, Source]