Martin Heidegger (1889–1976), who was born in Messkirch, Germany, on September 26 and died there on May 26, was among the most important thinkers of the twentieth century. His significance for science, technology, and ethics may be approached from four directions.

Theoretical Science and Practical Activities

Heidegger's first and still most important book, Sein und Zeit (1927; English trans. Being and Time, 1962), is a cornerstone of the existentialism that became prominent after World War II. The book's major terms—anxiety, resoluteness, everydayness, authenticity, concern, care, and the like—are concepts Heidegger helps make intellectually cogent. Albert Camus (1913–1960) and Jean-Paul Sartre (1905–1980) work on territory Heidegger opened up philosophically.

Martin Heidegger, 1889–1976. The German philosopher has become widely regarded as the most original 20th century philosopher. Recent interpretations of his philosophy closely associate him with existentialism (despite his repudiation of such interpretations) and, controversially, with National Socialist (Nazi) politics. (AP/Wide World Photos...