ON EXISTENTIALISM introduces the fundamental tenets of existentialism, focusing on the existentialist denial of the claim that the world is rationally structured. With reference to the seminal thinking of Nietzsche, Kierkegaard, Heidegger, and Sartre, the book is divided into two main chapters, one focusing on existentialist ontology and the other on existentialist ethics. Unlike most books introducing existentialism, ON EXISTENTIALISM is less concerned with presenting the reader with a wealth of detail regarding what the philosophers examined have said, but rather, is more concerned with presenting arguments for their most fundamental claims. THE WADSWORTH PHILOSOPHICAL TOPICS SERIES presents readers with concise, timely, and insightful introductions to a variety of traditional and contemporary philosophical subjects. With this series, students of philosophy will be able to discover the richness of philosophical inquiry across a wide array of concepts, including hallmark philosophical themes and themes typically underrepresented in mainstream philosophy publishing. Written by a distinguished list of scholars who have garnered particular recognition for their excellence in teaching, this series presents the vast sweep of today's philosophical exploration in highly accessible and affordable volumes. These books will prove valuable to philosophy teachers and their students as well as to other readers who share a general interest in philosophy.