In Farman's definition to "interface", which is a set of cultural relations that serve as the nexus of the embodied production social space(Farman, Mobile Interface Theory, 2012, p.64). And he further states that reciprocity between the embodied subject and an "ethical other" is very important, but what exactly is "ethical other"? 

From my understanding, the term refers to the other person who responses positively or negatively with the one who initiate the interaction, and then they form the reciprocal interaction. But why Farman put "ethical" to define the other person? What's the significance of the other being ethical?