In this paper, Iwill begin by providing an outline of the development of the theology of union with God, or theoric. I will have a particular focus on fourth-century Syrian monk Macarius-Symeon, whose Fifty Spiritual Homilies had an influence on early Pietism and early Methodism From there, I will seek to demonstrate how John and Charles Wesley, as well as their colleagues such as John Fletcher in the first generation of Methodist leadership, sought to critically fold this understanding into their own teaching regarding justification, sanctification and the ultimate goal of those who walk in union with God in Christ. Finally, this is integrated into a theology of mission in which this union with God is meant to be lived out individually and in community in a manner in which the missio Dei is extended in witness to the entire world.