''Hypostasis'' is not to be confused with God's essence/nature (''[[ousia]]'', i.e. what God is), or God's attributes (i.e. what God does).<ref>J.P. Farrell, "A Theological Introduction to the Mystagogy of St. Photios," in The Mystagogy of the Holy Spirit, ed. First M. Last Name (Brookline, MA: Holy Cross Orthodox Press, 1987), pp. 17-56.</ref>