In this chapter the authors argue that the human capacity for harming or else helping others flows from the same basic psychological group processes. They start by reanalyzing Milgram’s classic “obedience studies” in terms of “engaged followership”. This analysis suggests that participants obey toxic instructions to the extent that they see these as necessary in order to advance a worthy cause with which they identify. They argue that such engaged followership explains real-world as well as laboratory examples of harm-doing. They then reanalyze both laboratory and real-world examples of helping as engaged fellowship. This indicates that people aid others to the extent that they are construed as part of a common in-group. The difference between harming and helping, then, depends upon how one draws the boundaries of “us” and “them” and, hence, the extent to which one identifies with either perpetrating authorities or their victims.