The German philosopher and sociologist Jürgen Habermas challenged social science by suggesting that human beings are capable of rationality and under some conditions are able to communicate with one another successfully; the barriers preventing the exercise of reason and mutual understanding can be identified, comprehended, and reduced.

Jürgen Habermas was born in Düsseldorf, Germany, on June 18, 1929. At the end of World War II, he was repulsed by the Germans' "collectively realized inhumanity," which characterized, he believed, their lack of response to the revelations in the Nürenberg trials about the Nazi death machine. His own very different shock and horror constituted "that first rupture, which still gapes."

Entering the University of Bonn in 1946, he began to speculate about the meaning of such concepts as reason, freedom, and justice, in part by reading Hegel, Marx, and the Hungarian Georg Lukács...