With the publication of Reason and Existenz, originally delivered as a series of five lectures at the University of Groningen in 1935, one of the most important of Jaspers's philosophic works is made available to the English-speaking world. It concerns itself with a general statement of the principal philosophic categories which have given uniqueness to Jaspers's thinking: existence, freedom, and history, and the limit-situations of death, suffering, and sin.

Written shortly after Jaspers's major systematic work and before his analysis of the problem of truth, Reason and Existenz occupies a primary position in the development of his thought.