Is penal substitution consistent with divine simplicity?

It's important to keep in mind that Divine Simplicity, Divine Impassibility, and Penal Substitutionary Atonement are man-made theological constructs which attempt to codify the vast depth of God's revelation, making it easier to remember and apply but not necessarily fully encompassing all of God. We have been united with the mind of Christ but we are not yet made perfect and we are certainly not infinite in understanding. Theology must expect and even welcome uncertainty where the Divine being is concerned.

For God has consigned all to disobedience, that he may have mercy on all. Oh, the depth of the riches and wisdom and knowledge of God! How unsearchable are his judgments and how inscrutable his ways! “For who has known the mind of the Lord, or who has been his counselor?” “Or who has given a gift to him that he might be repaid?” For from him and through him and to him are all things. To him be glory forever. Amen. - Romans 11:32-36

Divine simplicity speaks of the attributes of God as being un-partitioned. In other words God is not like a Venn diagram in which some areas are just one attribute and other areas contain overlap between two or more attributes. It is unfortunate that a Venn diagram illustration of the Trinity is often used to try and clarify that doctrine of God's triune being because it visually and conceptually divides God into 3 parts with some overlap.

Divine Simplicity asserts that each attribute of God, for example Justice or Love, is entirely God or put another way, God is entirely each attribute. Notwithstanding that theologians dispute the various attributes ascribable to God, whatever attributes He does actually possess are, each of them, all God. Incidentally, assenting to this idea of Divine Simplicity ought to immediately make the Trinity acceptable if not completely ascertainable.

It is a biblically accurate idea:

Hear, O Israel: The LORD our God is one LORD. - Deuteronomy 6:4

This verse speaks of God not as an ordinal number but as an inseparably unique unity and it is valuable because it keeps us from imagining that God is somewhat like us with conflicting passions, strengths, and weaknesses. It can be difficult for us to grasp, however for two related reasons:

1. Often we erroneously conceive of certain attributes of God as opposite. For example we picture love and mercy being overcome or deferentially stepping aside as justice is dispensed. This is particularly evident when reconciling Divine Simplicity with Penal Substitutionary Atonement: Where has the love of God gone while divine justice is being dispensed? How is the one of whom God said, "This is my beloved Son in whom I am well pleased." now hanging upon the cross drinking to the dregs the undiluted cup of God's wrath? Human reason says it has diminished, departed, or been set aside. Divine simplicity declares it has not moved or changed in the slightest. In the cross is displayed God as Just and God as Love and not just portions of each. "God demonstrates his own love for us in this; while we were still sinners Christ died for us."
2. While we acknowledge God as infinite and eternal we do actually struggle to constantly and accurately incorporate these into all of our thoughts of God. If God is all of each of His attributes and He is infinite and eternal then He is infinitely and eternally each attribute as well. When Lamentations declares "His mercies never come to an end." it is drawing upon this principle of the infinity and eternality of each Divine attribute.

Divine impassibility is often considered as a corollary to simplicity because one attribute cannot trump another and force God's hand from within. Impassibility does not stem from simplicity, however, when declaring that God's hand is not forced from without; as if justice were a principle external to God which God is forced to obey. This blurring of distinction between Simplicity and Impassibility is a source of difficulty when Penal Substitutionary Atonement is considered. Let's look at the 4 questions again:

(1.A.) Are there versions of penal substitution which do not include recourse to a lack of emotional self-control – i.e. ‘needing’ to punish someone? This question introduces an assumption of emotional instability within the Godhead and makes the crucifixion of the Lord Jesus seem like a Divine reaction where some attributes overcome others. As the impetus to wrath is an internal one in this view, it is Divine Simplicity which provides the answer. "God IS light and in Him is no darkness at all." - 1 John 1:5. The (wrathful) expulsion of darkness from God's presence does not fall into the category of something forcing God to act or react. It emanates from His being. He IS the expeller of darkness infinitely and eternally.

(1.B.) How do they make sense of God’s anger/wrath in scripture? Prior to the foundational creative act it was already settled within the Divine Mind (Logos) that the Word of God would incarnate, bear humanity's sin, and redeem all creation.

Have this mind among yourselves, which is yours in Christ Jesus, who, though he was in the form of God, did not count equality with God a thing to be grasped, but emptied himself, by taking the form of a servant, being born in the likeness of men. And being found in human form, he humbled himself by becoming obedient to the point of death, even death on a cross. Therefore God has highly exalted him and bestowed on him the name that is above every name, so that at the name of Jesus every knee should bow, in heaven and on earth and under the earth, and every tongue confess that Jesus Christ is Lord, to the glory of God the Father. - Philippians 2:5-11

The Son’s eternal complicity in his own condemnation as our substitute is one of the gospel’s most glorious truths and it reverses the order in which we usually perceive Penal Substitution. Jesus Christ did not die as a Divine reaction to a creation gone bad. In the Divine economy of eternity Christ died, not so much first, as always. The Lamb was slain prior to the creation of time itself for God knows (not just intellectually but intimately and experientially) the end from the beginning. To be sure, "When the fullness of time had come, God sent forth His Son..." but this is just that, the appearance of the Christ in time...however his "coming forth is from of old, from ancient days. - Micah 5:2b". This "from of old, from ancient days" is a picture of "to the horizon, and again"...eternity.

This actually accentuates the love, justice, and mercy of God that He would pay so dear a price prior to creation and explodes the boundaries of grace when we realize that God did not have to create. This eternal grace of God in Christ displays every Divine attribute in full, impassible Simplicity not just in our redemption but in the whole of creation.

(2.A.) Alternatively, how do advocates of penal substitution communicate Christ’s work without seeming to violate divine simplicity/impassibility? The answers to 1 A and B show how Christ's work both displays and upholds simplicity/impassibility. No real resolution can be made without a robust and accurate Trinity. It’s no use pitting “vindictive God” against “innocent Jesus,” for the one nailed to the tree is himself the sin-hating, sinner-saving God.

(2.B.) Or do these concepts themselves need to be modified in light of penal substitution? Theological constructs of Simplicity, Impassibility, and Penal Substitution all need to be pressed deeper into the realms of infinity and eternality where God dwells in unapproachable light. The three are well demonstrated in Scripture and if they do not appear to harmonize with each other it can only be because our theological constructs of God, with whom is no variableness nor shadow of turning (James 1:17b), are limited and incomplete. As always, the center of the problem is that our God is not big enough: That is to say, the very act of trying to intellectually encapsulate Him is a diminution because the finite cannot contain the infinite. This is not to suggest that we cannot know God, after all He has condescended to reveal Himself, but the human heart wickedly seeks that complete understanding which indicates mastery and is a polluted manifestation of the naming power that God gave to Adam.

"I am the Lord, I do not change and therefore you are not consumed, Oh Jacob." - Malachi 3:6