Martin Heidegger (1889-1976) was a German philosopher, one of the most important and influential philosophers of the 20th century. His magnum opus Being and Time was devoted to the subject of ontology, or the study of being as such, and it is in this connection that he was a major influence on Jean Paul Sartre. He is thus widely considered one of the founders of existentialism, even though he never considered himself to be an existentialist.
Heidegger wrote books and essays on topics as varied as metaphysics, art, modern science, technology, language, the essence of truth, and the nature of thinking. But his most influential work, and that for which he is best known in the field of philosophy, is Being and Time, a massive tome in which he explores the question of being itself. Heidegger felt that western philosophy had strayed in ignoring this question while expending itself on individual cases of being (that is, on beings rather than being itself).
Through his work Question Concerning Technology (1953), Heidegger, though his name is far from as well known in conservation circles as those of Thoreau, Muir, or Leopold, can be considered one of the major theorists of the modern conservation movement. In this work, Heidegger sought what he called a "free relationship to technology", whereby mankind would neither automatically "opt for" nor automatically "opt out of" technological developments. In questioning technology, Heidegger helped lay the foundation for an ecological understanding of man's role in the world.
Heidegger's reputation has been clouded owing to his involvement with Nazism, beginning in the early 1930s while he was rector at Freiburg University. Although a post-World War II investigation held that his involvement was not of the "active" type, the controversy over the extent and nature of his support for the Nazis has not abated and has raised the question as to just how far it is possible to separate his or any individual's philosophy from his personal life.
The Catholic philosopher
Heidegger was born on September 26, 1889 in Messkirch, in southwestern Germany, the eldest child in a relatively poor Catholic family. After completing grammar school, he spent the next six years (until 1909) as a high school seminarian with the ultimate objective of entering the priesthood.
In late 1909, Heidegger became a Jesuit novitiate, but was soon dismissed for health reasons. Thereupon, he spent the next year and a half pursuing theological stuidies at Freiburg University. Again, however, his poor health intervened and he was forced to leave the seminary and abandon finally his plans for entering the priesthood.