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By 'radical,' I understand one who goes too far; by 'conservative,' one who does not go far enough; by 'reactionary,' one who won't go at all.

Woodrow Wilson (1916). “Wit and Wisdom of Woodrow Wilson: Extracts from the Public Speeches of the Leader and Interpreter of American Democracy, with Masterpieces of Eloquence”, Best Books
By 'radical,' I understand one who goes too far; by 'conservative,' one who does not go far enough; by 'reactionary,' one who won't go at all.