||In this paper we address the evolution of identity fusion. This concept is important because it offers the current best explanation as to why individuals can become empowered to act selflessly for a group, with both positive and negative implications. Using the evolution of cooperation (indirect reciprocity) we investigate minimal (i.e., low-cost) conditions under which identity fusion may be promoted. Indirect reciprocity is useful because it is reputation based, which can align to the identity of an individual, or that or a group. We introduce a formulation where individuals derive their personal reputation based on their level of identity fusion, and observe how identity fusion levels evolve under a range of conditions. In particular, we model a heightened sensitivity to vicarious hypocrisy due to identity fusion. We find that simple self-referential judgement and exclusion of perceived hypocrites during selection is sufficient to promote identity fusion. This is easily triggered by a sub-group of the population. Interestingly the self-referential judgement that we impose is an individual-level behaviour with no direct collective benefit shared by the population. The study provides clues, beyond qualitative and observational studies, as to how hypocrisy may have established itself to reinforce the collective benefit of a group reputation. This also provides an alternative perspective on the concept of controversial proposition group selection - showing how fluidity between an individual’s reputation and that of a group may function and influence selection as a consequence of identity fusion.