Existentialist anthropology is strictly connected with its ontology. The traditional distinction between soul and body is completely eliminated; thus the body is a lived-through experience that is an integral part of man's existence in its relationship with the world. According to Jean Paul Sartre, "In each project of the For-itself, in each perception the body is there; it is the immediate Past in so far as it still touches on the Present which flees it." As such, however, the body is not reduced to a datum of consciousness, to subjective representation. Consciousness, according to Sartre, is constant openness toward the world, a transcendent relationship with other beings and thereby with the in-itself. Consciousness is existence itself, or, as Karl Jaspers says, it is "the manifestation of being." In order to avoid any subjectivistic equivocation, Martin Heidegger went so far as to renounce the use of the term consciousness, preferring the term Dasein, which is more appropriate for designating human reality in its totality. For the same reasons, the traditional opposition between subject and object, or between the self and the nonself, loses all sense. Dasein is always particular and individual. It is always a self; but it is also always a project of the world that includes the self, determining or conditioning its modes of being.
All of these modes of being thus arise, as Heidegger shows in his masterpiece Sein und Zeit (1927; Being and Time, 1962), from the relationship between the self and the world. Heidegger has regarded concern (in the Latin sense of the term) to be the fundamental aspect of this relationship, insofar as it is man's concern to obtain the things that are necessary for him and even to transform them with his work as well as to exchange them so as to make them more suitable to his needs.
Concern demonstrates that man is "thrown into the world," into the midst of other beings, so that in order to project himself he must exist among them and utilize them. Being thrown means, for man, being abandoned to the whirling flow of things in the world and to their determinism.
This happens inevitably, according to Martin Heidegger, in inauthentic existence--day-to-day and anonymous existence in which all behaviour is reduced to the same level, made "official," conventional, and insignificant. Chatter, idle curiosity, and equivocation are the characteristics of this existence, in which "One says this" and "One does that" reign undisputed. Anonymous existence amounts to a simple "being together" with others, not a true coexistence, which is obtained only through the acceptance of a common destiny
All of the Existentialists are in agreement on the difficulty of communication; i.e., of well-grounded intersubjective relationships. Karl Jaspers has perhaps been the one to insist most on the relationship between truth and communication. Truths are and can be different from existence. But if fanaticism and dogmatism (which absolutize a historical truth) are avoided on the one hand while relativism and skepticism (which affirm the equivalence of all truths) are avoided on the other, then the only other way is a constant confrontation between the different truths through an always more extended and deepened intersubjective communication.
Jean Paul Sartre, however, denies that there is authentic communication. According to him, consciousness is not only the nullification of things but also the nullification of the other person as other. To look at another person is to make of him a thing. This is the profound meaning of the myth of Medusa. Sexuality itself, which Sartre holds to be an essential aspect of existence, fluctuates between sadism and masochism, in which either the other person or oneself is merely a thing. On this basis, the intersubjective relationship is obviously impossible.