Who or What is the Holy Spirit?

Medieval mystic Joachim of Fiore believed that human history was divided into three ages:

- The Age of the Father (a time of fear before Jesus)

- The Age of the Son (a time of faith following Jesus)

- The Age of The Spirit (a time of love when humanity would relate primarily to the third member of the Trinity).

He  predicted the final age would be a moment when churches, creeds, and  clergy would decline as people related to God more directly "as  friends."

Any of that sound familiar?