Overview: In contrast to empiricist and rationalist traditions, existentialism proposes and orderless world, vaguely hostile, where people choose their character goals, have an obligation only to "authentic," and may only observe the truth (reality) in moments of anxiety. In this program, University of California, Berkeley philosopher Herbert Dreyfus traces the roots of existentialism from Edmund Husserl's School of Phenomenology, to his pupil Martin Heidegger's theories of das Sein, the threefold structure of activity, authenticity, and nihilism. Dreyfus relates the philosophies of both en to present-day schools of thought.