Martin Heidegger (1889 - 1976) is acknowledged as one of the most important philosophers of the twentieth century. He wrote on a variety of subjects such as postmodernism, psychology, hermeneutics, political theory, existentialism, theology and phenomenology. He was also a member of the Nazi Party insofar as he was the rector at Freiburg University during the Nazi rule of Germany; something he later referred to as his 'political error'.
His major work was Being and Time (1927) which was fundamental in the development of existentialism - and many other strands of twentieth century thought - although Heidegger himself denied he was an existentialist.[Citation Needed]
Heidegger believed that a person's sense of self was dependent on a sense of time and his impending death.
The New American Desk Encyclopedia, Penguin Group, 1989