the Holy Ghost represents the final, complete stage in the evolution of God and the divine drama. For the Trinity is undoubtedly a higher form of God-concept than mere unity, since it corresponds to a level of reflection on which man has become more conscious.
Jung argues that the Trinity marks a decisive developmental advance in the God-image, its threefold structure corresponding to an expansion of human consciousness rather than a static theological abstraction.
, Psychology and Religion: West and East, 1958thesis