Now it gets tough.  That little baby wrapped in swaddling clothes and lying so cutely in the manger is the biggest trouble maker in world history, and the shocking claims that Christianity makes about who he is and what he means divide Christians not only from atheists and agnostics, but also splits Christians off from other religions.

If Christians saw that little baby as a beautiful symbol of human innocence and love, there would be no problem.  Even recognizing him as an important teacher and religious leader does not raise many hackles.  Islam recognizes Jesus as a prophet and the predicted Messiah; Islam has no trouble with the idea that he was born of a virgin, and the Virgin Mary is a popular and well respected figure for Muslims.

But that’s not how Christians see the baby in the manger.  They don’t think he is a symbol; they don’t think he’s a messenger.  They think he is the real thing.  He is the meaning of meaning, the truth made flesh, the only begotten Son of God.  As a grown man, he would tell people that “I and the Father are one.”  Christians believe he was right, and speak of the baby Jesus and the man he grew to be as one of the Three Persons of God.

For both Muslims and Jews, this an atrocious theological scandal, a fundamental betrayal of the essence of monotheism.  It’s not just that God is One and indivisible; while God is compassionate and caring there is an infinite distance between the Creator and the created, between God and man.  The Christian idea that Jesus is God, non-Christian monotheists feel, is a direct assault both on God’s unity and his transcendence.

For many Muslims, shirk, the improper association of the created with the creator, is the ultimate in blasphemy.  For many Jews, to worship a human being as God is idolatry – one of the worst sins there is.  Either the Christian belief about the baby in the manger is a monstrous error, or it is the most important thing in the world.

That’s not an argument we’ll be settling in this blog, but winning an argument isn’t what I’m trying to do.  My goal is to help Christian and non-Christian readers, whatever they think of the claim, understand what Christians mean when they make it. And so today I will be blogging about the mysterious and controversial Christian concept that lies behind this idea that the baby is God.  This is the Christian idea of the Trinity: the Christian belief that the One God of Abraham is not one person, but three — but that those three persons are one God, not three.

In the old days, almost every educated American, whether he or she were Christian or not, would have some idea about what this doctrine meant.  Not all Americans were Trinitarians; in addition to Jews and the very small number of Muslims in the United States at the time, Unitarians and Mormons also disapproved of the concept. But understanding this idea and at least something of its history seemed important enough both for the sake of understanding American history and culture, English literature, and world history, literature and art that even secular institutions of learning made some effort to inform their students about this idea.

That doesn’t happen much anymore, so let’s take a look at it here on the blog.

St. Patrick very famously explained the doctrine of the Trinity to new Irish converts by showing them a shamrock: three lobes, one leaf.  Others have used examples like a triangle: three sides, one figure.  None of these are exact, and Trinitarian theology is one of the most complex and arcane branches of Christian thought.  As a mere lay blogger I don’t have the theological chops to present a technically sophisticated and theologically nuanced presentation of the doctrine, so I’ll try to start from a different place – from this question of meaning that we have been tracing through Christmas.

I wrote earlier that theism is rooted in the intuition that the meaning we experience in our lives and our interactions with other people adds up to something real.  Love isn’t just a biologically conditioned feeling of affinity that encourages us to protect our children and other members of the tribe, assuring that our genes will be passed on in this brutally competitive world. Love in the Christian view is real; it reflects the basic nature of the universe and in the end love will be vindicated.

Like the other monotheistic religions, Christianity moves from the idea of meaning to the idea of a personal God, but Christianity goes a step further.  It identifies God with one particular aspect of meaning: love.  “God is love,” says one of the letters that make up the New Testament  (1 John 4:8). This is the phrase that Pope Benedict XVI chose for the title of his first encyclical letter; it resonates through the history and theology of all the Christian denominations like nothing else.

Christians really mean this.  When they say ‘God is love’ they don’t just mean that God is a being who loves.  They mean that love is the core of his nature, the key to his being.

Love isn’t something outside God; love is the nature of God.  And love is community.  Life isn’t life if it isn’t shared; to be God is to love.  God was love before there was a creation for him to be in love with; to be solitary is not in the nature of God.  Ultimately I think, what Christians mean by the doctrine of the Trinity is just this:  because God is love, community and relationship are rooted in the depths of his being.  Community is intrinsic to God.  His unity is communal.

There are two kinds of people who dislike this idea: rationalists and convinced monotheists who don’t buy the Christian package.  For rationalists, the idea that God is many and God is one is a contradiction and an absurdity. This was the part of Christianity that many of the Founding Fathers and other enlightened and educated people of the Age of Reason had the most trouble with.  They wanted a God who was logical; the Trinity didn’t fit.

Today, this is less of an issue.  We have all grown so accustomed to living with conflicting paradigms and grand narratives that we are less strictly logical than many of our ancestors were.  This isn’t always a good thing; a healthy dose of Aristotelian logic would clarify a lot of the confusions that vex our political and cultural discourse today.  There’s another, more creditable reason why the Trinity causes less intellectual conflict today: after even casually wrestling with modern physics, many people are more comfortable than they used to be with the idea that the basis of existence may violate human expectations and logical categories.  If light can be both particles and waves, maybe God can be both unitary and communal.

The other objection to the Trinity from the standpoint of other Abrahamic monotheisms remains vibrant and influential.  This is not a religiously polemical blog — at least I’m trying to keep it that way.  I can understand why people from other religious backgrounds and traditions see the Trinitarian idea as trying to chip away at the transcendence and the uniqueness of God, and I respect their concerns.  Christians, obviously, don’t share this objection.  For Christians, to say that the divine unity is so unimaginably deep, rich and transcendent that what humans understand as community is inextricably bound in God’s unique being is to stress his transcendence, not to undermine it.  Belief in the Trinity doesn’t, from this perspective, undermine one’s belief in the Unity of God: it gives our idea of God’s unity a depth that emphasizes just how unique and unimaginable the creator really is.

For Christians, God is a different order of being than we are, and one of the ways in which he is different is that for him there is no contradiction between the singular uniqueness of who he is, and the fact that his essence is community, relationship and love.

Christians see this communal nature of the one God as a further affirmation of the basic intuition of theism: that our experience of the meaning in life points us toward the divine.  People are social beings and much of the meaning and transcendence we find in life is related to our participation in social units ranging from the family to the global human community.  We are individuals, but we can only become our fullest selves in relationship with others.  God similarly is himself only in relationship; since God can never be less than fully himself, we must understand his being as complex enough to give full scope to this aspect of his being.

In any case, Christians describe God as a single being with three persons, usually referred to as the Father, the Son, and the Holy Spirit.  I’m just blogging Christmas here, not the whole Christian faith, so I’m not going to venture into this territory farther than to say that Christians believe that the baby in the manger was the second person of the Trinity: the Son of God.  As John Milton put it in his 1629 Nativity Ode:

That glorious Form, that Light unsufferable,
And that far-beaming blaze of Majesty,
Wherwith he wont at Heav’ns high Councel-Table,
To sit the midst of Trinal Unity,
He laid aside; and here with us to be,
Forsook the Courts of everlasting Day,
And chose with us a darksom House of mortal clay.