The helpful Quotations Page (http://www.quotation...opic.php?t=7641
) runs 'em down:
The phrase originated with Francois Guisot (1787-1874): "Not to be a republican at twenty is proof of want of heart; to be one at thirty is proof of want of head." It was revived by French Premier Georges Clemenceau (1841-1929): "Not to be a socialist at twenty is proof of want of heart; to be one at thirty is proof of want of head." Clemenceau supposedly said his version when he learned his son had just joined the Communist party: My son is twenty-two years old. If he had not become a Communist at twenty-two, I would have disowned him. If he is still a Communist at thirty, I will do it then.
Variations of the saying have occuured throughout history:
Aristide Briand (1862-1932): The man who is not a Socialist at twenty has no heart. If he is a Socialist at 30, he has no brain.
George Bernard Shaw in a lecture at the University of Hong Kong in Feb., 1933: Steep yourself in revolutionary books. Go up to your neck in Communism, because if you are not a red revolutionist at 20, you will be at 50 a most impossible fossil. If you are a red revolutionist at 20, you have some chance of being up-to-date at 40.
Benjamin Disraeli (attr.): A man who is not a Liberal at 16 has no heart; a man who is not a Conservative at 60 has no head.
Will Durant (1885-1982): There is nothing in Socialism that a little age or a little money will not cure.
Robert Frost, Precaution, (1936): I never dared be radical when young/For fear it would make me conservative when old.