
According to Thornhill (2008) Jasper's work is "a subjective-experiential transformation of Kantian philosophy, which reconstructs Kantian transcendentalism as a doctrine of particular experience and spontaneous freedom, and emphasizes the constitutive importance of lived existence for authentic knowledge." Jasper's most important philosophical work is His three volume Philosophy.
Each of the three volumes explores a different way of being: orientation (vol. 1), existence (vol. 2) and metaphysical transcendence (vol. 3). Jaspers considers these three ways of being as the essential existential modalities of human life.
Thornhill (2008) writes,
Each level of being in Jaspers' Philosophy corresponds to one of the Kantian transcendental ideas, and the modes of thinking and knowing defining each level of existence elucidate the intellectual content of Kant's ideas. The level of orientation in the world corresponds to the idea of the unity of the world; the level of existence corresponds to the idea of the soul's immortality; the level of transcendence corresponds to the idea of God's necessary existence. However, whereas Kant saw transcendental ideas as the formal-regulative ideas of reason, serving, at most, to confer systematic organization on reason's immanent operations, Jaspers viewed transcendental ideas as realms of lived knowledge, though which consciousness passes and by whose experienced antinomies it is formed and guided to a knowledge of itself as transcendent. Jaspers thus attributed to transcendental ideas a substantial and experiential content. Ideas do not, as for Kant, simply mark the formal limits of knowledge, marking out the bounds of sense against speculative or metaphysical questions. Instead, ideas provide a constant impulsion for reason to overcome its limits, and to seek an ever more transcendent knowledge of itself, its contents and its possibilities.
Ricoeur's first book following his World War II captivity was Karl Jaspers et la Philosophie de l' Existence, co-authored with his friend and fellow prisoner, Mikel Dufrenne. In the 1950's Ricoeur had the intention to complete a three-part work titled Philosophy of the Will. In reality only two sections of the tripartie conception were formally completed: The Voluntary and the Involuntary and Finitude and Guilt (two volumes Fallible Man and The Symbolism of Evil).
In an interview with Charles Reagan (1996), Ricoeur reveals both how Jaspers influenced this project and how part three Poetics of the Will was completed through other endeavors.
The trilogy that I proposed in the preface to the philosophy of the will is clearly inspired by the trilogy in the philosophy of Karl Jaspers. . . . In his trilogy, the first part was called "Exploration of the World," the second "Existence," and the third "Transcendence and Metaphysics." This is the format I planned for my future work. . . . I deviated from this plan because of the development of the philosophy of the will itself. That is to say, I began with a reflexive method borrowed from Husserl . . . . the continued goal is less important than the change in method . . . . what I call the grafting of hermeneutics onto phenomenology. . . . As for the third part of the plan . . . I would claim that what I have already called a poetics of the will was accomplished in other modalities. (pp. 123, 124).
Ricoeur, in his conversation with Reagan (1996) gives the example of three of his works which accomplish the third part of his initial plan. First, The Rule of Metaphor examines the creativity in language on the semantic level. Second, Time and Narrative is concerned with the creativity of language at the level of constructing plots, and third, Idelogy and Utopia is an investigation of the social imagination.
References
Reagan, C. E. (1996). Paul Ricoeur : His life and his work. Chicago: University of Chicago Press.
Thornhill, Chris, "Karl Jaspers", The Stanford Encyclopedia of Philosophy (Winter 2008 Edition), Edward N. Zalta (ed.)