The doctrine of the Trinity speaks of the divine nature of Christ (as in statement #2 in the barebones account I gave above, which says, "The Son is God"). It does not discuss the human nature of Christ. For that, we have to go to the doctrine of Incarnation. But of course the two doctrines are closely interconnected, because they are both about the same Christ.

One key way that connection is made is by the fact that both doctrines use the term "person." The orthodox doctrine of the Trinity teaches that in God there is one nature and three persons, whereas the doctrine of the Incarnation teaches that in Christ there is one person but two natures. Moreover, the one person of Christ is the same as the second person of the Trinity, the Son.

This may sound technical, but it actually clarifies things. It helps answer questions that people naturally want to ask once they learn the doctrine of the Trinity. For instance, let's go back to statement #2, and apply it to the man Jesus, and look at the questions that arise.

Key Christian belief: Jesus is God

Q: Does that mean Jesus is the same as God?

A: Yes and no. Jesus is God, but there is more to say about Jesus and God than just that.

1. There's more to say about God: For the Father is God (#1) and the Spirit is God (#3)

2. There's more to say about Jesus: for he is true man as well as true God.

Q: OK, so does that means Jesus is just part of God?

A: No, Jesus is God, not part of God.

For God has no parts.

The doctrine of the Trinity says the Father is God (#1), not part of God,

and the Son is God (#2), not part of God, etc.

That is why analogies for the Trinity like the three parts of an apple are just plain wrong.

The concept of Hypostasis.

To reinforce this point, Trinitarian doctrine needs a term that will indicate that Father, Son and Spirit are each a complete individual being, not a part of anything. That term is hypostasis. It is a very abstract term meaning, "complete individual being (of whatever kind)." E.g., my hand is not a hypostasis, but I am. My dog's ear is not a hypostasis, but my dog is.

Why do we need such an abstract term? Because we cannot use a term for some specific kind of being, such as dog or man or god. For three individuals of the doggy kind are three dogs, three individuals of the human kind are three humans, but the three divine hypostases are not three gods. The peculiar arithmetic of the doctrine of the Trinity, where one and one and one do not add up to three, makes it impossible to use specific kind terms, so we must use the most abstract term possible for "complete individual being (of whatever kind)."

The term Person

"Hypostasis" comes from Greek, "person" from Latin. For persona was the Latin term the Western church used to translate the Eastern church's Greek term, hypostasis. It is important to see that when the term persona was originally used in Christian doctrine, it did not mean "personality." It literally meant mask (from the Latin verb per-sonare, to sound through) but figuratively, it meant roles in a drama. For in ancient dramas, actors on stage wore masks. That's why, to this day, the cast of characters in a playbill is sometimes labeled dramatis personae, literally the masks of the drama.

So the term "person" is a reminder that in the drama of salvation narrated in Scripture, God appears as three different characters, three distinct individual beings: God in heaven, Christ on earth (who is then exalted to God's right hand) and the Holy Spirit given to the church. Each of these characters is a complete individual being who is fully God, not a mere mask or role. (In that sense, the ancient meaning of persona is be a bit misleading: the doctrine of the Trinity can't use any term of human language without bending it a little) . But neither does "person" simply have its modern meaning, as if it meant that God had three "personalities." Three different personalities would be three different Gods.

The concept of person or hypostasis is particularly important because it links the doctrines of Trinity and Incarnation. In the one doctrine, Christ is the second person of the Trinity. In the other, that same person is both God and man. The fact that the same person appears in both doctrines is the crucial link between the two doctrines, and indeed the crucial thing the church has to say about who Christ is: the same one (the same person or individual being) who is the eternal Son of God, begotten from the Father as the second person of the Trinity, is also God incarnate, true God and true man, born of the virgin Mary, crucified under Pontius Pilate, raised from the dead on the third day, and ascended in his human flesh to the right hand of God on high.

Dante's Analogy for the Trinity

In previous posts I've tried to convince readers that the analogies illustrating “how God is three and one” are not successful and also not very interesting, because the doctrine of the Trinity is not about how God is three and one. But for anyone who's still interested, I know of one analogy that's far better than the others. It's not exactly successful, because it's actually incoherent, but the incoherence reflects, in a material image, the strange arithmetic of the doctrine of the Trinity.

It comes from the last canto (chapter) of Dante's Paradiso, the final stage in his journey through hell, purgatory and heaven in his poem, the Divine Comedy, written in the early 14th century. Here at the end of the journey he tells of himself seeing God directly with his mind. He describes what he saw as a circle of light, consisting of three different colors, each filling the whole circle without being mixed up or blended with each other.

So imagine that: a circle of light, say green. And then light of another color, say red, completely filling the same circle—not just in one part of the circle while the green light is in another part. And then a third color, again filling the same circle completely. And yet the three colors remain distinct, each retaining its own integrity, not muddying each other up like when you mix different colored paints and get a nondescript brown. That distinctness, integrity and completeness is an image for how the Father is not the Son, the Son is not the Holy Spirit and the Holy Spirit is not the Father - - and yet there is only one God, one circle of divine light with three distinct colors, each of which fills the whole circle.

And then Dante sees something absolutely lovely about the second color, which it turns out is actually flesh colored, having a human face. And that of course, is an image of the incarnation.

The true mystery of the Trinity

In the previous post, I argued that the doctrine of the Trinity is not some inexplicable paradox about how God is three and one. This does not mean there is no mystery to the doctrine, but rather that the mystery lies elsewhere.

The church fathers (the theologians who articulated the doctrine in the 4th and 5th centuries) are very clear where the mystery is. They insist that God is incomprehensible precisely because of the mystery of the Trinity. But the mystery is not about how God can be three and one. The mystery is about the eternal begetting of the Son.

Unlike the notion of “three and one,” this mystery is stated right in the creed, which confesses that Jesus Christ is the Son of God, “eternally begotten from the Father.” For the word mystery, in its original sense, refers to a secret meant to be revealed (notice how the word is used in the New Testament, for example, in Eph. 3:4-6 or Col. 2:2). Like the rest of the doctrine of the Trinity, it is meant to be taught.

To see what it's about, you could start with the question, “Can God create God?” The orthodox Christian answer is No, because God is by definition uncreated (meaning that God has always existed, never came into being, was never created). Since God is uncreated, he can't be created—not even by God. (By the way, orthodox Christianity has no problem with the notion that God can't do what's self-contradictory—but that's a topic for another post).

So God can't create God. But what God can do is beget God. That's how the Son of God has his being: by being begotten, not created—as the creed says. He has his being from the Father, but like the Father, he has always existed, never came into being, was never created. The mystery is how he can originate from the Father even though he has always existed.

The mystery, in other words, is summed up in two words of the creed: “eternally begotten.” For you would normally think that begetting must be a process that takes time, and before you're begotten, you don't exist. The word “begetting” is just an old word for conceiving, in the biological sense. The way ancient biology thought about it, you could say: I was conceived by my father in the womb of my mother. And of course before that happened, I didn't exist.

But with the eternal Son of God, it's not like that. He has no mother, and he was begotten by the Father before all ages, so that there was never a time when he didn't exist. He is just as eternal as God the Father, even though he originated (was begotten) from the Father. When you track what the church fathers say about the incomprehensibility of God, this is always at the center of it.

But the mystery is not mere confusion. It is taught as Christian doctrine for good reason. And it has several consequences that are important to know about.

First of all, it means that the Son is just as eternal as the Father. So he is, in terms of his being, equal to the Father. To make this absolutely clear, the creed says he is “of one being with the Father” (you can also translate this, “of one essence”). This famous phrase is a sort of commentary on the statement that the Son is God (= statement #2 in my first post on the Trinity). It means he is just as fully God as God the Father is, and just as fully deserving of worship. So even though he originates from the Father, he is not less than the Father, as if he were some later, subordinate or second-rate god. All that follows from the fact that he is eternally begotten from the Father—begotten not created.

One last clarification. It is important to notice that everything we have said so far is about the nature of God, not about the human nature of Jesus. The doctrine of the Trinity has much to say about Jesus Christ, but it says it about his divinity, not his humanity. To talk about his humanity, you have to bring in the doctrine of the Incarnation. That's coming up soon in future posts on this blog.

But to get the essential gist of the difference between the two doctrines, Trinity and Incarnation, think of two births (as the 5th century church father Cyril of Alexandria put it). The one birth is eternal, when the Son of God is eternally begotten of the Father, as I've been describing in this post. The other birth takes place on Christmas day, when he is born of Mary, a baby boy laid in a manger. So in addition to the eternal birth of the Son of God, there is his temporal birth as the son of Mary. Two births: in eternity and in time. Two births, but only one person: the same person, the eternal Son of God, is eternally begotten of the Father before all ages and also born of the Virgin Mary on Christmas day.

To contemplate those two births is to enter into the deep and beautiful mystery of God.

It's not about "How God is Three and One"

The doctrine of the Trinity is a doctrine, which means a teaching—which is to say, it's supposed to be taught. So it's not something impossible to understand, which there's no point explaining. That notion, which you hear far too often, appears to stem from a misapprehension about what the doctrine actually teaches.

Most sermons I've heard about the doctrine of the Trinity begin by saying, “We can't explain how God is three and one,” and then proceed to avoid teaching the doctrine. The misapprehension here is that the doctrine of the Trinity is about “how God is three and one.” It's not. The doctrine of the Trinity is about how God is Father, Son, and Holy Spirit—just like the creed says.

Of course, if you bother to count, you get three. There is also the affirmation that is a genuine part of the doctrine of the Trinity, which is that there is only one God (see statement # 7 in the previous post). So you can go ahead and say God is three and one, if you want. That's true. But it's not what the doctrine of the Trinity is concerned with. The doctrine of the Trinity is summarized in the creed, which never once uses the word “three.” In other words, you can be a perfectly fine believer in the doctrine of the Trinity without ever in your life hearing about God being three and one. So no sermon on the doctrine of the Trinity needs to explain “how God is three and one.” If you're a pastor, you can feel free to just drop that subject and forget about it.

What a sermon on the doctrine of the Trinity does need to explain is the creed. What I've provided in the previous post (the seven statements I stole from Augustine) is simply the logical bare bones of the creed's teaching. To put flesh on those bones, study the creed and its Scriptural sources. But for now, let me point out some features of those logical bare bones.

First of all, despite what you may have been told in so many sermons, it's not all that confusing. Each individual statement is quite clear, using extremely simple language: no reference to “essence” or “substance” or any technical terms like that. Those terms are needed to explain why adherents of the creed reject various heresies, but they're not needed for a basic statement of the doctrine itself.

Of course, it's true that the arithmetic doesn't add up. If you bother to count, you get something like a paradox. (It turns out, it's not a strict logical paradox: in some systems of logic, which use a non-standard identity operator, the seven statements come out as logically consistent. It's sort of a technical way of forgetting to count. This is possible, because in modern formal logic you can do logic without incorporating arithmetic.) But the simplest thing to do, if you're not a formal logician, is just don't bother to count.

The simplest and most widespread misunderstandings of the doctrine of the Trinity come from people who try to provide analogies for how God is three and one, such as the three parts of an apple (skin, flesh and core) or the three forms of H2O (water, ice and steam). A telltale feature showing why these analogies are wrong is that they “add up” arithmetically, thus getting rid of what they're trying to explain. If you try to follow the logic of these analogies very far, you end up just getting the doctrine of the Trinity wrong.

For instance, God is not at all like the three parts of an apple. The reason why can be seen by looking closely at the first three of the seven statements. They're simple, but they're exact. They don't say: (1) The Father is part of God, (2) The Son is part of God and (3) The Holy Spirit is part of God. God has no parts, and the doctrine of the Trinity never says he does. It says (1) The Father is God, (2) The Son is God and (3) The Holy Spirit is God.

Likewise, God is not at all like three forms of H2O. For the Father is not one form of the same God as the Son and the Spirit. Again, the Father is God, the Son is God, and the Holy Spirit is God. That's what the doctrine of the Trinity teaches, quite emphatically and quite clearly.

And with no confusion. If you try to count, then you can get confused, and that's when you'll be tempted to use bogus analogies to “explain” the doctrine. But leave out the number three, and the basic logic is very clear. The Father is God. He is not part of God or a form of God or a representation of God or a way we experience God anything fancy like that. He simply is God. And the same with the Son. And the same with the Holy Spirit. That's statements 1-3.

Then go on to statements 4-6, which simply point out the difference, making it clear that Father, Son and Holy Spirit are not three names for the same thing. Again, note how very simply it is said:

4. The Father is not the Son

5. The Son is not the Holy Spirit

6. The Holy Spirit is not the Father.

Then add monotheism. For though the word “three” is not important in the doctrine of the Trinity, the word “one” is:

7. There is only one God.

To clarify what's odd about the arithmetic here, just imagine we weren't monotheists. Then we could say something like:

1. Jupiter is God

2. Neptune is God

3. Vulcan is God

Then, distinguish the three of them:

4. Jupiter is not Neptune

5. Neptune is not Vulcan

6. Vulcan is not Jupiter.

Then, of course, you would go on and say what the doctrine of the Trinity does not say:

7. There are three Gods.

The interesting question about the doctrine of the Trinity is not how God is three and one, but why Christians would want to say something as strange as those seven statements about Father Son and Holy Spirit, which don't add up. To explain that, you have to start talking about Jesus Christ, who is at the heart of Christian faith. For what the doctrine of the Trinity really is, is the doctrine about who God must be if Christ is really and truly God, as Christians believe.

Doctrine of the Trinity: the bare bones

I've found that most Christians have not been taught in church or school who God is, according to the Christian faith. So here is a one page handout I use in class to explain the basics of the two most fundamental Christian doctrines, which are both about who God is. I stole the seven statements from Augustine, by the way. The next post will add some commentary.

The Two Basic Christian Doctrines

The two most important Christian teachings are about who God is and who Jesus is: the doctrine of the Trinity and the doctrine of the Incarnation.

A. The Doctrine of the Trinity can be summed up in 7 statements:

1. The Father is God

2. The Son of God (i.e. Jesus Christ) is God

3. The Holy Spirit is God

4. The Father is not the Son

5. The Son is not the Holy Spirit

6. The Holy Spirit is not the Father

7. But there is only one God.

The logical paradox here is simply that the arithmetic doesn't work out right. After confessing these Three as God (1-3) and distinguishing each one from the others (4-6), we conclude by saying they do not add up to 3 Gods.

But notice that aside from the strange arithmetic, the doctrine of the Trinity is stated above in very simple terms. This statement is based on the way the Bible talks about God the Father, about Christ, and about the Holy Spirit. You only have to use fancy philosophical language (like "essence," "substance," and so on) in order to argue against certain complicated heresies. Using that language, the Church traditionally teaches that in God there is only one essence (or substance or nature) but three persons. This language goes back to the Nicene Creed's homo-ousios clause, which says that Christ is of one substance or essence with the Father. This clause is basically a comment on statement number two: it means that when we say Christ is God, we mean he is God in exactly the same sense that the Father is.

B. The Doctrine of the Incarnation or "Christology" is the basic Christian teaching about who Jesus is. After saying that he is God (in the doctrine of the Trinity, above) we go on to say that he is a human being as well, just like us. Thus in a nutshell, the doctrine of the Incarnation teaches:

Jesus Christ is both true God and true man.

Using philosophical language again, the Church traditionally says that Christ is one person having two natures (i.e. both divine nature and human nature).

By the way, the doctrine of the Incarnation does not explain how this is possible; it just says that's how it is. But in saying so, it does rule out certain common mistakes. For instance, many people will say, "Jesus can't really be God; he's too human." But according to the doctrine of the Incarnation, that's a mistake: since Christ is both true God and true man, the fact that he is truly human doesn't make him any less truly God.

Likewise, his being truly God does not make him any less human. He is not simply God looking human. Nor is he simply God taking over a human body: being true man, he has everything that belongs to human nature, including a human soul as well as a human body. Of course he has no sin, but his lack of sin is not inhuman but rather makes humanity what it was always meant to be.

Welcome to Theological Questions

This blog is for people with theological questions, especially Christians interested in Christian doctrine. I get many questions from people who have listened to my courses for The Teaching Company on Augustine, Luther, Philosophy and Religion in the West, and The History of Christian Theology. And now I'm beginning to get questions from readers of my new book, Good News for Anxious Christians (Brazos Press, 2010).

I always try to answer these questions drawing on resources from the central teachings of the Christian tradition, though I'm also not averse to giving my considered judgment on controversial issues or even wading into the middle of a debate when I think a lot is at stake. Hence I will start this blog by posting material I use in classes to present fundamental Christian teachings like the doctrine of the Trinity—which, oddly, most Christians have never been taught. (It's extraordinary, and encouraging to me as a teacher, how hungry people are to learn these things!) But then I will proceed to more controversial topics, like why the recent evangelical attempts to revive subordinationism in the doctrine of the Trinity are a deep mistake.

So, welcome to the blog.

Phillip Cary