The addition of the filioque clause to the nicene creed by the western church aka the Catholic Church was a major reason that the unified Church broke into east and west i.e. Orthodox and Catholic, of course Papal supremacy also led to the churches breaking into schism as well, but its hard to maintain that the Orthodox don't actually have the legitimacy claim since the filioque clause is in fact a departure from the creed and how can churches that claim the creed not actually follow the real cr