The Great Christmas Mystery

Advent (meaning “coming”) is the season of the church year in which Western Christendom celebrates the coming of Jesus Christ into the world.1 This festive winter season precedes and extends beyond Christmas, which is the specific day chosen to honor Christ’s birth.

Doctrinally speaking, the great mystery behind Advent and Christmas is what Christians call the incarnation. This biblically derived truth teaches that the eternal Word or Son, the second person of the Trinity, took unto himself a human nature and became human without in any way diminishing his deity.

Consider these two biblical passages:2

In the beginning was the Word, and the Word was with God, and the Word was God. . . . The Word became flesh and made his dwelling among us. We have seen his glory, the glory of the one and only Son, who came from the Father, full of grace and truth (John 1:1, 14).

Who, being in very nature God, did not consider equality with God something to be used to his own advantage; rather, he made himself nothing by taking the very nature of a servant, being made in human likeness (Philippians 2:6–7).

This theological understanding of the incarnation led the ancient Christians to refer to Jesus as the theanthropos (Greek: the “God-man”). Borrowing from the fourth-century Christian church father Athanasius, C. S. Lewis unpacks the theological meaning of Christmas in a single sentence:

“The Son of God became a man to enable men to become sons of God.”3

The Visited Planet
But Christians are so used to hearing about the incarnation at Christmastime that it’s easy to take this reality for granted without considering its extraordinary magnitude. The incarnation means that God walked the earth in the person of Jesus Christ. Thus, Earth is the divinely visited planet.

The magnificence of the incarnation is reflected well by NASA Astronaut Jim Irwin, who was part of the Apollo 15 crew in 1971. He compared his time on the Moon with Jesus’s time on Earth:

“God decided that He would send His Son Jesus Christ to the blue planet, and it’s through faith in Jesus Christ that we can relate to God . . . As I travel around I tell people the answer is Jesus Christ [and] that Jesus walking on the earth is more important than man walking on the moon.”4

The Grandest of Mysteries
Theologian J. I. Packer says of this biblical claim that “Nothing in fiction is so fantastic as is this truth of the Incarnation.”5

Yet skeptics dismiss the incarnation as just one more fictitious story. According to their naturalistic worldview, miracles by definition only happen in mythology. But that’s an inherent assumption, not a demonstrable fact. In contrast, if it’s reasonable to conclude that a God exists, then miracles would be an expected feature of this theistic worldview.

The New Testament Gospel accounts as narratives don’t fit the typical mythical genre. Instead, even with the miracle stories contained therein they still read like actual historical accounts. And as Packer states: “The incarnation itself is an unfathomable mystery, but it makes sense of everything else in the New Testament.”6

This mystery is ours to contemplate and cherish, at this time of year and always. As the Advent carolers sing: “Joy to the world, the Lord is come.”


  1. The equivalent of Advent in Eastern Christendom is known as Nativity.
  2. For two other explicit biblical statements about the incarnation see Colossians 2:9 and 1 John 4:1–3.
  3. C. S. Lewis, Mere Christianity (New York: Macmillan, 1952), 154.
  4. Clare Bruce, “An Encounter with God on the Moon: Astronaut Jim Irwin’s Incredible Lunar Experience,” Hope 103.2, July 19, 2019; See also Jim Irwin and William A. Emerson Jr, To Rule the Night: The Discovery Voyage of Astronaut Jim Irwin (Philadelphia: A. J. Holman Co, 1973).
  5. J. I. Packer, Knowing God, anniversary ed. (Downers Grove, IL: InterVarsity, 1993), 53.
  6. Packer, Knowing God, 54.