Jean Wahl 
Philosophies of Existence [PDF ebook] 
An Introduction to the Basic Thought of Kierkegaard, Heidegger, Jaspers, Marcel, Sartre

This book, first published in 1969, examines the ‘philosophies of existence’ or Existentialism and the field’s leading philosophers. These philosophers, the book argues, wished to distinguish themselves from other philosophies in their structure and approach – and it is that structure that this book takes care to analyse.