Gregory of Nissa’s Against Eunomius can be analyzed as a paradigmatic work of the comparison between theology and philosophy and thus effective also in highlighting the potential and the limitations of other systems for theology, as in for example Complexity Theory. Such a theory lends itself to the need to contextualize every theological statement in an horizon of relation (of place, of time, of person). At the same time however, complexity cannot demand, neither in a theoretical nor in a practical sense, to be the ultimate key to understanding the investigated reality, be it human or divine.