The most fundamental attribute of God’s being is its simplicity.
God is “simple” in the sense in which the word is used in chemistry—his nature is not compounded of different elements.
An analogy with water may help us to understand what this means and why it matters. Water is a compound substance made up of hydrogen and oxygen, and it can be separated into its component parts.
God is not a compound. If he were, he could not be the ultimate being. His parts would all be logically prior to him. Presumably there would also have to be some force that produced “god” out of those different parts, and that force would also be a greater being than the resulting “god” is. Such a being does not and cannot exist, and therefore we have to say that God is “simple”—he is what he is, and that is all there is to it.
Divine simplicity means that whatever we say about God applies to the totality of his being. God is not partly invisible or partly immortal. When we meet with God, we meet with him in the fullness of his being, because he cannot be anything less than that. There is much about God that we do not know, but we can be certain that whatever is hidden from our eyes is consistent with what has been revealed to us. Paul told the Corinthians: “Now we see in a mirror dimly, but then face to face. Now I know in part; then I shall know fully” (1 Cor. 13:12). In other words, we have partial knowledge of the fullness of God, not full knowledge of only a part of him. That knowledge will expand, but as with an image in a mirror, it will come into better focus, not be something completely different from what we already know.
Divine simplicity also means that God’s attributes interpenetrate each other. Theoretical analysis is useful because it allows us to concentrate on different aspects of his being, but we cannot extract one attribute, like invisibility, and treat it as if it had nothing to do with the others. Whether we think of God as immortal, impassible, or eternal, what we say about him is true of everything in him. If God is righteous, then he is immortally and eternally righteous. If he is impassible and invisible, then his righteousness is also impassible and invisible.
Divine simplicity prevents us from calling personality a divine attribute. If it were, there would be only one person in God, not three.
Simplicity also makes it impossible to say that God is wrathful by nature. Wrath is the way disobedient people experience God’s justice, but it is not a divine attribute. If it were, God would be angry with everybody all the time.
In these and other similar ways, simplicity serves as a check on our analysis of God’s being and helps us to understand what can (and cannot) be classified among his attributes.
God’s simplicity is not explicitly mentioned as such in the Bible, but it is consistent with what James says about the Father of lights, “with whom there is no variation or shadow due to change” (James 1:17). James is speaking primarily about God’s consistency in giving gifts to his people, which will never be diminished or taken away, but he justifies that statement by referring to the nature of God, which is consistent with itself.
The doctrine can also claim support from a number of biblical passages that say things like: “Hear O Israel, ‘The Lord our God, the Lord is one’” (Deut. 6:4, quoted by Jesus in Mark 12:29).
Isaiah 44:6 goes further and says, “I am the first and I am the last; besides me there is no god.”
And this statement is echoed in Revelation 1:8, where God reveals himself to John as the Alpha and Omega, the first and the last.
Another important verse is Ephesians 4:6: “one God and Father of all, who is over all and through all and in all.”
None of these texts speaks directly of the divine simplicity, but they all bear witness to God’s oneness and exclusiveness—there is no other god besides him.
Properly understood, “simplicity” covers both “unity” and “perfection,” terms that have sometimes been used to indicate divine attributes thought to be distinguishable from it. In reality, they go together. If God is who he says he is, then his simplicity ties everything together, and as James put it, there is no variation in him.