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This question is asking whether God is formally the goodness of all things. Note, this is not asking whether God is the exemplar of the goodness of things (He is) or the goodness of all things in the sense of a final cause (He is), but, is asking whether every goodness is formally God. To illustrate, the fire communicates the form of heat to a certain pot of boiling water. The fire is the cause of the heat of the water and the exemplar of that heat, yet, the heat is something communicated and outside of the fire who possesses the heat principally. This consideration should clear up all confusion concerning this question.