Why do people celebrate Christmas?

It’s the time of year when we explain what Christianity is about.

God exists

Basically, we know from a variety of scientific arguments that the universe was created and fine-tuned for life by an intelligent agent that existed causally prior to the beginning of the universe, because this agent brought the universe into being. Our purpose as humans is to enter into a two-way loving relationship with this Creator/Designer of the universe. This is the only way that we can ultimately be happy and fulfilled.

We avoid God

Now, when you look at human experience, none of us is interested in finding out about the character of this Creator/Designer, because we are afraid that if we find out too much about him then we will have our freedom to do as we please constrained by the demands of a relationship with an all-powerful, all-good being. Just knowing that such a person exists and has a character distinct from our own is enough to cause us to flee from him so that we can stay autonomous from the obligations of the moral law that he expects us to follow.
Christians believe that this universal desire to avoid an all-powerful, all-good God who will judge us is a result of bad behaviors inherited by us from the very first rebellion against God by our ancestors. Ever since that rebellion, the capability for relating to God has been lost, because we no longer have the ability to stop our rebellion against God. Christians call the first rebellion of our ancestors “The Fall of Man”.
What does this rebellion look like for us today? Well, we want to do whatever we want, in order to be happy, and to ignore God’s demands. We want to have happy feelings, including security, community and being morally good, all without a relationship with God. We want to acquire and rearrange matter for our selfish ends without acknowledging and honoring the Creator/Designer of that matter. And, of course, we would like other people to affirm, voluntarily or involuntarily, that our rebellion against God is really the height of moral goodness.
Additionally, some people imagine that God, if he exists at all, must desire our happiness. And of course when their needs are not met by this invented God, then they become even more bitter at God, and eventually decide that God could not really exist since their selfish needs are not being met by him. It never seems to occur to us humans that some pain and suffering may be permitted by God in order to turn our attention away from pleasure and security in this life, and back towards a relationship with him.
This is the mess we find ourselves in. This propensity for turning away from God and trying to pursue selfish happiness and security apart from a relationship with God is what the Bible calls “sin”. Every single one of us deserves severe punishment for refusing to pursue a genuine two-way love relationship with the God who is there. That is the mess we are in before Jesus appears to address this problem.

Jesus saves the day


I cannot say much about how Jesus solves the problem of rebellion against God, because that is really the
story of Easter, and today we are dealing with the story of Christmas. But I can say that the solution to the problem requires that God step into history to communicate with his creatures and to perform actions in order to be reconciled with them. That is the message of Christmas: God is stepping into history to do something to end our rebellion. Easter is the story of what he does.
This is talked about in the Bible in John 1, for example.
John 1:1-5:

¹In the beginning was the Word, and the Word was with God, and the Word was God.

²He was with God in the beginning.

³Through him all things were made; without him nothing was made that has been made.

⁴In him was life, and that life was the light of men.

⁵The light shines in the darkness, but the darkness has not understood it.

You can substitute the word “Word” there for Logos, which really means logic or reason or wisdom. This is a person with a divine nature, identified with the eternal being of God, who exists causally prior to the creation of the universe, who is going to take on an additional human nature, including a human body. (Christians believe that there is one divine “what” being and three divine “who” persons). Software engineers, you can think of Jesus having two natures as multiple inheritance in C++.
And it continues in John 1:10-14:

¹⁰He was in the world, and though the world was made through him, the world did not recognize him.

¹¹He came to that which was his own, but his own did not receive him.

¹²Yet to all who received him, to those who believed in his name, he gave the right to become children of God—

¹³children born not of natural descent, nor of human decision or a husband’s will, but born of God.

¹⁴The Word became flesh and made his dwelling among us. We have seen his glory, the glory of the One and Only, who came from the Father, full of grace and truth.

Here the word grace doesn’t mean like a graceful ballet dancer. It means an instance of mercy received from a superior. A person (a “who”) identified with the divine being (a “what”) has decided to make us a top-down offer of mercy.
The same message of God stepping into history is found in the Christmas carols that people sing at Christmas.
Christmas carols
Here’s the best one, “O, Holy Night“, and it says:

O holy night! The stars are brightly shining.
It is the night of the dear Savior’s birth.
Long lay the world in sin and error pining,
Till He appeared and the soul felt its worth.

When we were in rebellion, we had lost our most valuable capacity – the capacity of being in a direct relationship with God. And if the newborn baby Jesus can accomplish his mission (and he did), then we are going to regain that capacity for a direct relationship with God.
Now look at “Hark! The Herald Angels Sing“, which one of my favorites:

Hark! The herald angels sing,
“Glory to the newborn King!
Peace on earth and mercy mild,
God and sinners reconciled.”

Basically, as I often say, there are only two kinds of people in the world. There are people who are willing to respond to the offer of a relationship with God, with all the little sacrifices and compromises that a relationship entails, and then there are people who are not willing to respond. For the people who are willing to respond, the appearance of Jesus is the best thing that could possibly happen, because now we are finally going to have a chance to deal directly with God, face-to-face, to find out what he is like, and change ourselves to be more like him, with his help.
And that is why people celebrate Christmas. It’s the anniversary of the birth of Jesus. It is the story of God stepping into history to be reconciled with his rebellious creatures. It’s the story of the divine Logos subjecting himself to the life of a creature in order to rescue us from our sinful, self-destructive rebellion. This love for undeserving creatures is above and beyond the call of duty. We didn’t love him, but instead he loved us first, and he loved us enough to come down here and suffer with us so that we could be reconciled with God.
MERRY CHRISTMAS!