Concept

Lesson 2.3, The Doctrine of God

Intro

What kind of God does Christianity claim? Not just one god out of many. Not just the biggest version of a human person. Not just a wise spiritual presence behind nature. The historic Christian answer is more specific, and the specifics matter.

The tradition calls God Being Itself. He does not exist the way a chair exists or the way a star exists. Everything else that exists depends on Him to keep existing. He does not depend on anything to exist. He is necessary, eternal, unchanging, and holy. He is the source from which everything else draws being.

This way of describing God is called classical theism. The first part of this lesson walks through the attributes that belong to God alone, sometimes called the "incommunicable" attributes: aseity (God exists from Himself), immutability (God does not change), eternality (God is not in time the way we are), simplicity (God is not made of parts), infinity. The second part walks through the attributes that have a created echo in us as image-bearers, the "communicable" attributes: knowledge, goodness, love, wisdom, justice.

The third part takes up the Trinity, the doctrine that the one God exists in three Persons, Father, Son, and Holy Spirit. This is where the Christian doctrine of God parts ways with every other monotheism. The Trinity is not a math puzzle to be solved or a confusion to be cleared up. It is the claim that the God who is one in Being is also eternally three in Person, and that this is the deepest truth about who He is.

Why all the care? Because the modern alternatives (theistic personalism, deism, pantheism, polytheism) each take a piece of the historic doctrine and change it in a direction the tradition has rejected. To know what Christianity claims about God, the historic categories are not optional decoration. They are the claim itself.

In full

The first structural commitment of Christianity is the doctrine of God. Historic Christianity has called this classical theism. God is not one being among others. He is not the biggest member of the class of existing things. He is not a maximally great person scaled up from human persons. He is Being Itself, the necessary, simple, eternal, unchanging, holy source of everything that is. The historic tradition works this out with a care most modern believers do not have. The care matters because the alternatives, theistic personalism, deism, pantheism, polytheism, each take one piece of the historic doctrine and change it in a direction the tradition has rejected.

This lesson walks through the incommunicable attributes (those that belong to God alone), then the communicable attributes (those that have echoes in us as His image-bearers), and finally the Trinitarian elaboration that sets the Christian doctrine of God apart from every other monotheism on offer.

Required reading

Classical Theism, the codex's master page for the classical view. Start here. This page is the spine of the lesson. Everything else fills in detail.
Trinity, the master hub for the Trinitarian doctrine. One God, three Persons, homoousios, eternal processions, immanent and economic Trinity. After Classical Theism, this is the second reading.
Classical Theism vs Theistic Personalism, the side-by-side comparison with the modern alternative. Read this third. It shows what the historic doctrine rules out by way of contrast.

The incommunicable attributes

The historic tradition splits God's attributes into two groups. Incommunicable attributes are ones God has in His own being that cannot be shared with creatures. Communicable attributes have echoes in creatures made in God's image. The incommunicable set is what makes God God and not just a very impressive creature.

Aseity, aseitas, "from-Himself-ness." God exists necessarily, of Himself. He is not caused by anything else. He does not depend on anything else for His being. He could not have failed to exist. Every creature exists contingently, could have been otherwise, depends on God for being. Aseity is the floor under every other divine attribute. The Yahweh of Exodus 3:14, I AM WHO I AM, is the biblical revelation of aseity in personal form.
Divine Simplicity, God is not made of parts. He is not body plus soul. He is not essence plus existence. He is not substance plus accidents. He is not a bundle of separate attributes. His attributes are not parts of Him. They are identical with His being. God is His goodness. God does not have goodness as a separable quality. This sounds abstract until you notice what it rules out: any view of God on which one of His attributes could exist apart from another, or on which He could lose an attribute without ceasing to be God. Simplicity is what holds the other attributes together as one.
Eternity, God is not inside time. He does not experience one moment after another the way creatures do. He does not wait for the future to arrive or watch the past slip away. The classical statement (Boethius) is interminabilis vitae tota simul et perfecta possessio, "the complete and perfect possession all at once of unending life." This is not timelessness in the sense of being frozen. It is the fullness of God's life held in a single eternal now.
Immutability, God does not change in His essence, His attributes, or His purposes. He is not improved by His relations with creation. He does not learn. He does not regret in the sense of being caught off guard. The biblical language of "God repented" (Gen 6:6, 1 Sam 15:11) is the picture-language of relational change from the creature's point of view, not metaphysical change in God's own being. Immutability follows from simplicity and aseity. A simple, self-existent being cannot gain or lose what it is.
Actus Purus, actus purus, "pure act." This is Aquinas's technical term. God has no unrealized potential. Every creature is a mix of actuality and potentiality. A tree is actually green and potentially red. A person is actually awake and potentially asleep. God is purely actual. There is no "potential God" waiting to be realized. There is no further state He might become. He is fully Himself, eternally, with nothing missing.
Impassibility, God is not subject to passions in the technical sense. His being is not pushed around by outside causes the way creaturely emotions are. He is not made angrier by being provoked the way humans are. His love is not increased by being loved back. This does not mean God is cold or distant. The biblical revelation overflows with God's affective life. It means that affective life is active, not reactive. It comes out of God's eternal character. It is not caused by the creature's effect on Him.
Omnipresence, God is wholly present at every point in space, not spread out across space the way a body is. He is not "in" the universe the way a fish is in water. The universe is "in" Him the way an effect is in its cause. The traditional formulation: God is present essentialiter, praesentialiter, potentialiter, by His essence, by His presence, by His power.
Infinity, God is not limited by anything. He is not limited by space (omnipresence). He is not limited by time (eternity). He is not limited by another being (aseity). He is not limited in His attributes (each is infinite, infinite holiness, infinite love, infinite power, infinite knowledge). Infinity is the language of unbounded perfection, not a quantitative scaling-up of finite categories.

The classical doctrine holds all of these together. Pull on one and the others come with it. This is the deep philosophical work the patristic and medieval tradition did. It is what Theistic Personalism modifies in a direction the historic tradition has resisted. The contrast is the substance of this lesson's comparative reading. The Classical Theism vs Theistic Personalism page lays it out.

The communicable attributes

The communicable attributes are ones that have echoes in creatures made in God's image. The echo is real but partial. Humans are not just smaller versions of God. The divine reality is the source and the human is the image.

Holiness, God is set apart, in being and in moral character. He is not in the same category as creatures. He is the Holy One who alone is to be worshipped. In Scripture, holiness is the attribute the heavenly creatures cry out three times, holy, holy, holy (Isa 6:3, Rev 4:8). It is the attribute that most directly marks God as God in the creature's experience.
Love, God is love (1 John 4:8), not merely loving as a contingent attitude toward creation. This is one of the places where the Trinity becomes load-bearing. God's love is internal to His own life from eternity (Father, Son, Spirit in mutual love). It is not a property He picks up by having someone to love. The communicable echo in humans is real love but always a copy of the divine original.
Goodness, God is goodness itself, the summum bonum. Every created good shares in His goodness. Nothing is good apart from Him. The Euthyphro dilemma, is something good because God wills it, or does God will it because it is good?, is resolved on the classical view by the identity of God's nature with goodness itself: God wills the good because He is good.
Justice, God gives each what is due. This is the attribute that grounds final judgment, the seriousness of sin, and the need for atonement. It is not arbitrary punishment. It is the moral order of the universe expressed in personal terms.
Mercy, God's love directed toward the miserable. It is His refusal to give what is strictly due in justice. Mercy is not opposed to justice. At the cross they meet. The atonement is where God's justice is fully satisfied and His mercy fully extended in a single act.
Truth, God is true in His being and in His word. He does not deceive. He cannot lie (Heb 6:18, Titus 1:2). The reliability of Scripture, the trustworthiness of God's promises, and the apologist's confidence in revelation all rest on this.
Wisdom, God orders all things to their proper ends. Wisdom is not just intelligence. It is the practical ability to bring about the right outcomes through the right means. Creation, providence, and redemption are all expressions of divine wisdom.
Omniscience, God knows all things. Past, present, future. Actual and possible. The heart of every creature. This is not the result of His learning. It is internal to His being. The classical and Molinist traditions debate exactly how God's knowledge relates to creaturely freedom, but the fact of exhaustive knowledge is shared.
Omnipotence, God can do all things consistent with His nature. He cannot make a square circle (not because of a limit on His power, but because the phrase names nothing). He cannot lie (not because of weakness, but because it would contradict His truth). The historic tradition has held this carefully. Omnipotence is not arbitrary will. It is maximal power exercised in accordance with the divine nature.

The communicable attributes are where the apologetic conversation lives most often. The atheist asks about God's goodness in the face of evil. The Muslim asks about God's justice and mercy. The pluralist asks about God's love for non-Christians. Each of these conversations requires the apologist to hold the classical-theistic frame so the attributes are not collapsed into their human caricatures.

The Trinitarian elaboration

Christianity is a monotheism, Hear, O Israel, the LORD our God, the LORD is one (Deut 6:4), but a monotheism of a particular shape. The one God exists eternally as three Persons: Father, Son, and Holy Spirit. One ousia (being), three hypostases (persons), distinguished only by relations of origin.

One ousia. The three Persons share, fully and identically, the one divine nature. The Son is homoousios, of the same being as, the Father. This is the bright line the Council of Nicaea (AD 325) drew against Arius. Arius held that the Son was of similar being (homoiousios) but not the same. One iota's difference in the Greek. An infinite difference in the theology.
Three hypostases. The Persons are really, eternally distinct. Not three modes of the one God showing up one at a time (the modalist error). Not three gods cooperating (the tritheist error). The Father is not the Son. The Son is not the Spirit. The Spirit is not the Father.
Distinguished only by relations of origin. The Father is unbegotten. The Son is eternally begotten of the Father. The Spirit eternally proceeds from the Father (and, in Western theology, from the Son, the filioque). All three are equally God, equally eternal, equally to be worshipped. Their distinction is relational. It is not a difference in being or power.

The Trinity is what sets Christianity apart from unitarian monotheisms (Judaism, Islam) and from every form of pantheism, polytheism, and modalism. See Trinity vs Oneness vs Modalism vs Arianism for the side-by-side comparison. See Trinity for the master hub. See Tawhid for the Islamic doctrine of God's absolute unicity, which is the Trinity's most carefully-developed monotheistic rival.

The relation of the Trinity to the divine attributes above is integration, not addition. Aseity, simplicity, eternity, immutability, and so on are attributes of the one divine nature shared by all three Persons. The Trinity is not a fourth thing added on top of the doctrine of God. It is the form the one God's being takes in eternity. This integration is what makes the historic Christian doctrine internally coherent. It is what the modernist alternatives often quietly drop.

Key takeaways

Classical theism is the doctrine of God the historic Christian tradition has confessed. Aseity, simplicity, eternity, immutability, actus purus, impassibility, omnipresence, infinity. These attributes hang together. Pull on one and the others come with it.
The communicable attributes are real echoes in creatures, but copies. Holiness, love, goodness, justice, mercy, truth, wisdom, omniscience, omnipotence. The human echo is real but partial. The divine reality is the source.
Theistic Personalism is the modern alternative, and the historic Christian doctrine is not it. Theistic personalism scales God up from human personhood. Classical theism does not scale God up from anything. Know which one you confess and why.
The Trinity is the form the one divine nature takes in eternity. One ousia, three hypostases, distinguished only by relations of origin. Not three gods (tritheism). Not one god in three modes (modalism). Not a hierarchy (Arianism). The full equality and full distinction of the three Persons is the historic confession.
The Trinity is what makes Christianity not Islam, not Judaism, not Unitarianism, not pantheism. The doctrine is not optional decoration on a generic monotheism. It is the structure of the Christian doctrine of God.

Worked example, the divine attributes at work in a single text

Read Hebrews 1:1-3 with the attributes in mind.

"God, after He spoke long ago to the fathers in the prophets in many portions and in many ways, in these last days has spoken to us in His Son, whom He appointed heir of all things, through whom also He made the world. And He is the radiance of His glory and the exact representation of His nature, and upholds all things by the word of His power..." (Heb 1:1-3, NASB95)

Aseity, "God... has spoken." The God who speaks is the one who exists in Himself, prior to and independent of those He addresses.
Trinity, God spoke... in His Son. The Father and Son are distinguished as speaker and locus of speech. Both are God.
Eternity and creation, through whom also He made the world. The Son is the agent of creation, sharing the Father's eternity prior to creation.
Divine simplicity, the exact representation of His nature. The Son is not a part of God or a mode of God. He is the exact image of the one divine nature.
Omnipotence, upholds all things by the word of His power. Holding the universe in being is itself an exercise of omnipotence.
Glory and holiness, the radiance of His glory. The Son's nature shines with the holiness of the Father.

One passage. Six attributes. All assumed by the writer as the background of his argument. This is the doctrinal density the apologist needs to recognize when the conversation moves to specific texts.

Reflection questions

Can you state three of the incommunicable attributes in your own words, without slipping into a theistic-personalist reading? (The test: does your statement of "eternal" mean "lasts forever in time" or "outside time entirely"? Does your statement of "immutable" mean "never changes His mind" or "is not subject to metaphysical change in His being"? The first answer in each pair is the personalist reading. The second is the classical.)
What hangs on divine simplicity? Most modern Christians have never thought about it. Walk through what changes if God is made of parts, and notice that you have left classical theism behind.
Hold the Trinity formulation in your head for sixty seconds without slipping. One God, three Persons, distinguished only by relations of origin. The Son is eternally begotten of the Father. The Spirit eternally proceeds. One being, three relational subsistences. Most beginning Christians drift into modalism, tritheism, or Arianism within thirty seconds. The discipline is the practice of not drifting.
Which of the communicable attributes do you find hardest to integrate with the others? Many Christians struggle to integrate love and justice, or mercy and holiness. The integration is in God's own being. It is not a tension we resolve from outside.

Practice exercise

Pick three of the incommunicable attributes (aseity, simplicity, eternity, immutability, actus purus, impassibility, omnipresence, infinity). Draft a one-paragraph defense of each in your own words. The paragraph should: (1) state the attribute clearly, (2) distinguish it from the modern personalist alternative, (3) give one biblical text that anchors it, (4) note one common objection or misunderstanding. Then run all three past a serious Christian peer or pastor and ask: where would a thoughtful Muslim, atheist, or theistic personalist push back? Refine the paragraphs against the pushback. Repeat until you can deliver each in under ninety seconds without notes.

Next lesson

→ Continue to Lesson 2.4, Christology in One Lesson.