Rationalist

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.

-- Sir Karl Raimund Popper (1902 - 1994), Austrian and British philosopher and a professor at the London School of Economics, Utopia and Violence (1947)