Abstract: The article summarizes some comments -as discussed in my book La existencia en busca de la razón. Apuntes sobre la filosofía de Karl Jaspers (Existence in search of Reason. Notes on Karl Jaspers' Philosophy), Editorial Académica Española, LAP LAMBERT Academic Publishing GmbH&Co. KG, Alemania, 2012- about the meaning of the boundary situations in the philosophy of Karl Jaspers, as a turning point regarding Husserl's phenomenology and Kant's transcendental philosophy. For Jaspers, the meaning of the boundary situations as a structure (...) of Existenz underlines the possibility of risk in the individual historicity, which breaks the "flow" of the reflection and, at the same time, appeals to an opening of ethics -without sacrificing the universality of the categorical imperative. (shrink)