Jaspers defines his philosophy as philosophizing, in order to emphasize the practical function of thisthinking. His approach to philosophy evokes many similarities with the ancient concept of philosophy as wisdom related to life, the art of living. And yet, although the similarities are suggestive, it is the dif- ferences that come to the fore. This is because Jaspers’ formula of philosophy is a thoroughly modern and original proposition, differing from ancient con- cepts in its basic tenets, as I shall demonstrate. I highlightthe differences by identifying two assumptions underlying this concept: the “source of thought” (der denkende Ursprung) and the “thing” (Sache), that the man has made his. The concept of the practical function of philosophy belongs to one of the many paradoxes found in Jaspers’ thought. I follow the mystery of this para- dox by juxtaposing Jaspers’ concept of practical philosophy against its ancient predecessor, based on several selected categories, such as freedom, reason, fear, real life, and philosophical meditation that the two seem to share. Along the way, I argue that the contemporary formula of Jaspers’ practical philosophy gives the original and modern shape to the eternal idea of philosophy as the guide to life.