DIVINE SIMPLICITY & THE INCARNATION

Question #33: How can the singularly unique, simple God immutable and impassible become incarnate in Jesus Christ, truly assuming a finite, passible human nature, yet remain uncompromised in His divine simplicity?

A core challenge in Catholic theology is reconciling how the second Person of the Trinity can truly assume a human nature with all its limitations and susceptibility to suffering without fragmenting or altering the divine essence. Since divine simplicity insists God has no parts to be added or changed, and divine impassibility asserts that He cannot undergo suffering in His divinity, the Incarnation can seem like a contradiction. Yet Christological doctrine, especially as defined at Chalcedon in 451 AD, clarifies that Jesus Christ is one Person, the eternal Son, who unites both a fully divine and a fully human nature. In light of this, it helps to see God as having eternally and fully realized His own life in a single, timeless act, since He is inconceivably perfect and beyond all limitation. Whereas our existence is fragmented and bound in time, God stands outside those constraints. In His perfect fullness, He is already supremely free and superabundantly loving as Father, Son, and Holy Spirit. Therefore, He can graciously assume a truly human nature, not from any inner lack, but out of love. He remains unchanged in His divine essence, yet freely unites Himself to our finite reality to accomplish His redemptive will in time.

By way of analogy, God, standing outside of constraints, is freely consistent with whatever He is. I like to think of it like pollution. In California, where I live, there are signs warning of pollution fines of $1,000 or more for littering on the side of the road. I often think: can a human really pollute the entire universe, with its possibly infinite size and scope, compared to us little humans and our earthly problems? The point of this analogy is that it would be a category mistake to suggest localized pollution could somehow corrupt an infinite universe. To me, it seems even more absurd to think this could apply to the super-essential and superabundant Triune God, who is infinitely beyond the universe itself.

God’s Simplicity and the Two-Natured Christ teaches that the single divine Person of the Son assumes a real human nature, body and soul, rather than mixing or blending it with His divinity. In doing so, the Son remains simple, immutable, and impassible in His Godhead while personally possessing a truly human mode of existence. The addition of this human nature affects only the created reality taken on, not the uncreated divine essence. Hence, there is no composition introduced into the Godhead, and Christ retains two distinct natures in one Person without confusion or division.

Distinguishing Divine Immutability from the Human Capacity to Suffer clarifies that while Jesus genuinely experienced suffering, growth, and death in His human nature, the Son’s divinity is neither altered nor made passible. He freely wills to suffer through His assumed humanity. The humanity truly undergoes hunger, pain, and distress, but the divine essence remains untouched by these experiences. Known in Catholic tradition as the communicatio idiomatum, this principle preserves the property of each nature: the Son as God remains impassible, but as man He truly endures human suffering.

The Incarnation as a Free Assumption, Not a Divine Deficiency underscores that nothing compels God to become incarnate. He does so out of pure generosity rather than any inner lack. Since God is already infinite fullness, He gains nothing by taking a human nature. Rather, He acts out of love for the sake of our redemption, as seen in John 1:14 and Philippians 2:5–8.

Christological Union without Violating Simplicity explains that Catholic orthodoxy consistently affirms one Person in two natures, with the divine essence remaining indivisible. The Incarnation changes the state of human nature by uniting it to the Person of the Son, not the uncreated Godhead itself. This preserves the Son’s eternal, simple being while allowing the fullness of divinity to dwell bodily in Christ.

By upholding both divine simplicity (God’s essence is indivisible, immutable, and impassible) and the hypostatic union (two natures in one divine Person), Catholic theology teaches that God does not compromise His own simplicity when becoming incarnate in Jesus Christ. The Son truly suffers in His humanity yet remains unchanged in His divinity, so that the immutable, impassible God fully enters our human condition for our salvation. One additional-and final- nuance is that this union is not a temporary arrangement but a permanent self-giving of the eternal Son. Far from contradicting divine simplicity, the Incarnation shows that God’s love, already complete in itself, freely embraces and redeems our finite existence without ever ceasing to be the utterly simple and unchanging source of all being.

(see #16 and #28 for further background)