Modalism is a word unfamiliar to ordinary Christians. This is unfortunate in a way that I want to explain the next several days. The word modalism may not be widely known but the idea is the most common theological error among people who believe they are fully orthodox. Modalism, in brief, is the idea that the three persons in the Trinity are different modes of God’s activity rather than separate/distinct persons.
Subordinationism taught that the second and third persons of the Trinity were in a secondary relationship to God the Father. Modalism tended toward a denial of any distinction between God and Christ. It taught that there was one absolute God, and thus the Father, Son and Holy Spirit were three different modes (“forms”) of God. In this view God shows himself under three names just as an actor might wear three different masks to play three different roles (persona) in a play. The most common way that I hear this idea illustrated is in analogies people employ to talk about the Trinity. A common one is to speak of me, for example, as one person while at the same time I am a father, a son and a brother. But this idea is clearly not faithful to the biblical doctrine of Trinity. I hope to show you why by explaining the problem of modalism.
Why is modalism so popular? It is the simplest way to explain the Trinity while at the same time preserving the oneness of God. Adoptionism preserved the unity of the godhead by sacrificing the deity of Christ. Modalism preserves the unity of the godhead by abandoning the personhood of Christ and the Holy Spirit but by affirming deity strongly. Modern conservatives often fall into this trap because they do insist on the deity of Christ but then have little or no grasp of the doctrine of the Trinity to support that belief.
Modalism thus occurs among conservatives precisely because in upholding the deity of Christ they do fail to see him as a distinct person vis-à-vis the Father. The modalist sees the Father at work in creation and in giving Israel the law. Modalism sees the Son coming to live and die for our salvation. And it sees the Holy Spirit coming after Christ’s ascension to reveal him to us and to live his life in us. Modalsim thus correctly avoids the idea that Christ is a second God alongside the Father. So what is the essential mistake here? Modalism abandons the diversity of persons within the godhead and thus loses the core biblical idea that Christ is our representative (advocatus) with the Father.
Modalism logically leads to the notion that the events of redemptive history are a kind of divine charade. Since the Son is not a distinct person in modalism he cannot fully represent us before the Father. But this is just the beginning of the problems this thinking causes. Modalism is also docetic. Docetism taught that Christ only appeared to be human. He was human in appearance only, not in his essence. If he was divine then God died on the cross and God cannot die. The consequence of all this is to believe that while Christ died he could not have been truly human. He only appeared to be human. This is a major error and one that has wreaked havoc in conservative understanding. It undermines the uniqueness of our message in a way that makes it less able to affect the whole human person who is redeemed by the fully human Christ.