Sir Karl Raimund Popper

A rationalist, as I use the word, is a man who attempts to reach decisions by argument and perhaps, in certain cases, by compromise, rather than by violence. He is a man who would rather be unsuccessful in convincing another man by argument than successful in crushing him by force, by intimidation and threats, or even by persuasive propaganda.

Karl Popper, “Utopia and Violence,” an address to Institut des Arts in Brussels, Belgium (1947), published in Conjectures and Refutations: The Growth of Scientific Knowledge (1963).