It is sociologically very significant that isolated elements are unified by their common relation to a phenomenon which lies outside of them. This applies as much to the alliance between states for the purpose of defense against a common enemy as to the "invisible church" which unifies all faithful in their equal relation to the one God.

DEFINE: Simmel is articulating a principle of unification: shared relation to something external draws disparate elements into a coherent whole.

Georg Simmel, The Sociology of Georg Simm…, loc. 4202