I guess that you will mean otherness, alterity, condition of being another or relationship to each other or another one from me. This concept has been studied philosophy, psychoanalysis and the social sciences with very different perspectives. Focusing on the other and not in the other, this can be seen as an equal with whom they collaborate or as an adversary against which defend themselves. A philosophical analysis of alterity or otherness is reflected in the dialectic of master and slave of the phenomenology of the spirit of Hegel.
