Weber also proposed a socio-evolutionary model of religious change, showing that in general, societies have moved from magic to polytheism, then to pantheism, monotheism and finally, ethical monotheism.[22] According to Weber, this evolution occurred as the growing economic stability allowed professionalisation and the evolution of ever more sophisticated priesthood.[23] As societies grew more complex and encompassed different groups, a hierarchy of gods developed and as power in the society became more centralised, the concept of a single, universal God became more popular and desirable.[24]