A contrast heralded in the phenomenology of Husserl and Heidegger, and central to Sartre's work Being and Nothingness . Being for-itself (pour-soi ) is the mode of existence of consciousness, consisting in its own activity and purposive nature; being in-itself (en-soi ) is the self-sufficient, lumpy, contingent being of ordinary things. The contrast bears some affinity to Kant's distinction between the perspective of agency or freedom and that of awareness of the ordinary phenomenal world.
Philosophy dictionary. Academic. 2011.