The Holy Spirit is the principal agent of the mission to evangelize in the world of the present. However, sometimes little is understood about the foundations of the Church's mission and evangelization in relation to the Holy Spirit. This is a book intended to articulate, clarify and refine the understanding of this vital relationship. In this way, the call of the Church to be faithful and discerning of her mission may always be lived inspired by the light of the undying fire, the Holy Spirit.