William Hasker (Metaphysics and the Tri-Personal God) cites Carl Mosser’s objection to social Trinitarianism’s claim that the three Persons are “distinct centers of willing”: “If the divine persons cannot differ because they necessarily act in concert with one another, then attributing distinct wills is superfluous. Attributing distinct wills to two or more persons simply is an admission of the possibility of difference. If there can be no difference, then the individuals share a single will” (206).
Hasker responds by noting different senses of the word “will”: “it can refer to the content of one’s will (the state of affairs that is willed), or to the act of willing, or to the faculty or capacity of willing.” He takes Mosser’s claim to mean that “if it is impossible for there to be a difference in the content, then there cannot be more than one faculty of willing” (206).
This doesn’t seem to follow. He asks us to consider two lovers: “They have the same content of will—that each shall love the other. Does that cast any doubt whatever on the fact that each has his or her own distinct capacity of willing? To be sure, given the reality of human weakness, there is the possibility of inconstancy. But now suppose that, beginning at the moment when love first awakens, each is for all eternity so appealing to the other that no deviation from perfect mutual devotion is possible. Furthermore, this same mutual devotion guarantees that, for all eternity to come, neither will oppose or impede anything desired by the other. Do these suppositions cast any doubt whatever on the assumption that there is a distinct faculty of will for each of the lovers?” (206).
Hasker glosses: “Father, Son, and Holy Spirit all will that the Son shall become incarnate. So far, there is ‘one will’ between them. The Son, however, wills to become incarnate (or, that I shall become incarnate)—something that is not willed by either the Father or the Holy Spirit. If the Son’s faculty of will were not distinct from those of the Father and the Spirit, the Son could not in this way will something not willed by the Father or the Spirit—namely, to become incarnate” (206-7).
By the same token, he argues, refusing to acknowledge distinct acts and faculties of will “would also negate the mutual love between Father and Son, for the act of will involved in loving another simply cannot be the same act as that involved in the other’s love for oneself” (207).
One way to avoid this is to claim that no Person can think or say “I.” But then, who does?