This concept stems from the philosophy of existence of Karl Jasper. Contrary to objects of investigations and variations the actual situation in which man exists cannot be perceived as object among other objects. Every try to declare the own situation as object is confined through the experience of ones own finiteness. Boundary situations are opaque and inevitable. To them belongs the being-in-a-situation itself, the dependence on chance, fight, death, suffer, guilt and death. Border situation may help to become conscious of the loneliness and suspiciousness of being and to risk the leap from an possible to a true existence in freedom.