Amyraldism, otherwise known as ‘four-point Calvinism’, has long been seen by many as a compromise position between Reformed and Arminian theology. I disagree with this characterization, but I do find Amyraldism problematic theologically. John Samson, in ‘The Amyraldian View Undone’ (HT: Charlie Ray):
How is it possible to contend that God gave His Son to die for all men alike and for the same purpose, and at the same time grant the redemptive benefit of effectual grace (for which Christ died to procure) only for some which He would select? Have you ever considered that effectual grace is also a redemptive benefit for which Christ died? What is Christ’s relation to this effectual grace four-point Calvinists speak of? Is this grace (that Amyraldians affirm) to be found outside of Christ? Or in Christ? Surely it is not a Christless grace but they have effectually removed Christ from the equation by not linking effectual grace with the atonement. The Trinity works in harmony and God saves his people through Christ’s redemption, not outside of it. So if this grace is found in Christ then Christ died in a way for the elect (to procure effectual grace) that He did not for the non-elect.
The Amyraldian view of the atonement in the predestinarian scheme, according to B. B. Warfield, ‘is a logically inconsistent form of Calvinism and therefore an unstable form of Calvinism’: indeed, ‘it turns away from the substitutive atonement, which is as precious to the Calvinist as is his particularism, and for the safeguarding of which, indeed, much of his zeal for particularism is due.’
The instability, as I see it, extends beyond the doctrine of substitution and strikes at the heart of the Trinity itself. The Father elects men to final salvation; the Son accomplishes atonement; the Holy Spirit applies redemption by persuading and changing the human heart. If the intent of the atonement cannot be said in any way to be limited to the unconditionally chosen elect, we suddenly have a Father with a limited electing decree and a Holy Spirit who acts accordingly but a Son who, in making universal atonement, effectively does his own thing.
To put it in nerdy terms, what we say about the trinitarian œconomy impinges on what we say about the trinitarian ontology. A double-minded Trinity is unstable in all his ways, which instability is incompatible with orthodoxy. The problem, theoretically, may be more serious than Nestorianism, which separated the one person of the Christ into a divine and a human hypostasis (substance): Amyraldianism threatens to separate the Son himself from the rest of the Trinity, making the Godhead itself an entity of of multiple beings. This would make the Christian faith a polytheistic religion.