 There are several other significant entries into the group selection discussions, including the book, Unto Others: The Evolution and Psychology of Unselfish Behavior (Sober &amp; Wilson 1998). Here, a case for group selection is developed based on the need to account for the existence of biological altruism. Biological altruism is any behaviour that benefits another organism at some cost to the actor. Such behavior must always reduce the actor’s fitness but it may (following the work on interdemic selection), increase the fitness of certain groups within a structured population. There was a big benefit to bringing the attention of the larger philosophical community to group selection models, and explaining them in an accessible fashion. It has thus brought this aspect of the units of selection controversy out onto the main stage of philosophical thought.