This hymn sets up some of the themes of my argument, so please listen to it first!
I take Christian Unitarianism to be the conjunction of the positions that Jesus of Narazerth is the Messiah by whose death and resurrection salvation entered the world, and that Jesus of Nazareth is not the same being, substance, or person as God the Father. Christian Unitarians can take a variety of positions with respect to Christology, e.g. the view that Jesus was fully human and led a sinless life, and was elevated to a divine-like status, that Jesus was an angelic being, Michael for example, who took on flesh, or that Jesus was a lesser deity who existed prior to creation eternally or before creation began, i.e. he was the Logos, which should be construed as a demiurge who acted on behalf of an utterly transcendent higher God.
First, I should motivate some aspects of my premises regarding the nature of God. Though we cannot understand God fully, I do believe that the Christian God is that being than which none greater can be conceived. If Christian Unitarians reject that definition, that’s fine, but I also think that the Anselmian God actually exists, and anything that is not this “Anselmian God” is a false god who is unworthy of worship.
Second, 1 John 4:8 tells us that God is love. Given that the Anselmian God is the greatest conceivable being, and that love is a perfection, it stands to reason that if there is an Anselmian God, that God exemplifies a love than which none greater can be had. Otherwise, one might easily conceive of a greater God.
So the argument is this:
D1: God is that than which none greater can be conceived. [Anselmian definition]
P1: If God is that than which none greater can be conceived, God exemplifies that love than which none greater can be had.
C1: God exemplifies that love than which none greater can be had. [From D1 & P1 MP]
D2: That love than which none greater can be had is laying down one’s own life for a friend. [Definition from Jn 15:13]
P2: If Christian Unitarianism is true, it is not the case that God exemplifies laying down one’s own life for a friend.
C2: If Christian Unitarianism is true, it is not the case that God exemplifies that love than which none greater can be had. [From D2 & P2]
C3: Christian Unitarianism is false. [From C1 & C2 DN + MT]
Some possible responses:
1: On Trinitarian Christianity, God did not exemplify that love than which none greater can be had until 33AD. Therefore, God is not the Anselmian God, since a God that has laid down his own life for a friend for a greater amount of time is greater.
R1: God is an eternal and omniscient being. In creating the World, and from His perspective, the Trinitarian God already exemplifies this love for all time. From all time, his sacrifice is exemplified. Temporally, it happened for us on a particular date in history. Moreover, Christ laid down his life for all, including past humans. That the act of laying down one’s life for a friend did not happen at the earliest moment of history does not cheapen the act, since an earlier sacrifice would not have been for more “friends.”
2: The Trinitarian God only laid down his life once. One could conceive of a God who lays down his life more times. So the Trinitarian God is not the Anselmian God.
R2: The quantity of times one lays down one’s life is not the issue, but when it is done for a friendship. Christ died that all may be counted as friends. And he did this in friendship and obedience to the other persons of the Trinity. Thus, there is no “friend” for whom Christ could lay down his life a second time. The fallen angels are forever enemies of God by their will, so they are not among the set of possible friends for whom God could lay down his life again.
3: John 15:13 is really about the greatest act of love a human can do, not the greatest act any “one” can do. Or Christ was using hyperbole. Or the act does not include God, who is capable of a higher act of love. Or it is logically impossible for God to exemplify this human act of love.
R3: The Greek in John 15:13 doesn’t limit the case to humans, but just uses the pronouns “οὐδεὶς,” “τις,” and “αὐτοῦ.” These are reasonably translated as “no one,” “one,” and “of him.” So it isn’t clear from the text that the case is limited to human beings. Given that Christ would go on to lay down his life for humanity, it would be strange to think that he was just being hypebolic here. If he were being hyperbolic and there is some greater act of love, what is it? What act of love does God do that would be greater than had he laid down his life for our salvation? The burden would be on the Christian Unitarian to make the case that some other act of love is greater, despite the Scripture. Finally, if it is argued that it is simply logically impossible that God lay down his life for a friend, then this puts the Christian Unitarian in the uncomfortable position of trying to demonstrate that the incarnation is a logical absurdity. Some might take up this task, but it is not an easy task.
With respect to my response to the third objection, I would like to emphasize a couple of other issues. A) It seems to me that one of the beautiful messages of Christianity is this theodicy, if it can be called a theodicy, that doesn’t seek to explain away evil, but says that God entered into this veil of tears too. God humbled himself and experienced evil directly. Christian Unitarianism seems to cheapen this “theodicy” because it tells us that God remains distant and somehow thinks sending someone on his behalf is “good enough.” Relatedly, B) Christian Unitarianism tells us that the death of one sinless human (or semi-divine being) was sufficient to atone for sin. On theories of the atonement, like the satisfaction theory, this cheapens the debt of sin. On Trinitarianism, a divine person of the Holy Trinity, laid down his life for us all. The life of the Second Person of the Holy Trinity is His own. No creature can claim to own his or her life in the same way a divine, necessary, and eternal being can. So, if Christ were just another creature, the offering of his life would be less significant. It would be offering something that, in some sense, belonged to the Father in the same way any other creaturely life belongs to the Father. If the Unitarian chooses to escape this by positing a co-eternal, necessarily existing per se, lesser divinity (polytheism), this conflicts with aseity, which is arguably a great-making property. Also, such a move seems ad hoc, since I don’t think any Christian Unitarians would say that the Logos is per se necessary, i.e. necessarily exists of itself and not by the necessity of the Father (higher God).
There is one last objection that occurs to me (though there may be others):
4: Even if God exemplifies the highest form of love through Christ’s sacrifice, on Trinitarianism, it is only one persons of the Trinity who exemplifies this love. The Father and the Holy Spirit either cannot, or do not exemplify this love.
R4: Being of one substance, God can be said to exemplify this love. And this love is exemplified to a higher degree since one being exemplified it, not merely through one person, but all three. For it is the Father who sent the Son, and it was by the Power of the Holy Spirit that the Son became incarnate. Thus the supreme act of love is one act by one Being who, being multi-personal, stands in different relations to the act. The Father sends the Son, which is the very act by which the Son is sent by the Father. And this is the act by which God so loved the World (Jn 3:16). Whether the Father or the Holy Spirit could have incarnated instead of the Son is an interesting question. But, if my earlier point is correct, it is not a supreme act of love to merely lay down one’s life. So only one of the Persons could have done this if the act was for all “friends.” A second passion via another Person of the Trinity would not affect anything more for God’s friends. So it is not necessary that God exemplify this sacrifice by all Three Persons laying down incarnated lives. Once was sufficient, and all three persons were completely involved in the event, though by different relations.
Thanks to Andrew Terrell for a conversation which helped stimulate some of these thoughts. Though, I should say that any heretical views expressed here are my own.