"I love Christmas,” writes Bruce David Forbes. “And Christmas drives me crazy.” With that opening confession, he sets out to determine just how much of the holiday is real after all—whatever real means. The skimpy biblical accounts, decidedly pagan revelry, manufactured nostalgia and commercial overlay all raise his eyebrows. Even though Forbes’s tone is never sardonic, his “candid history” does make clear that from the start Jesus has been just one reason for the season.

Much of what we love about Christmas predates Christianity. As Forbes notes, the Roman midwinter festival Saturnalia closely resembled the modern holiday, with weeks of eating and drinking, gift giving, wreaths of evergreens, and concern for the less fortunate. A Scandinavian midwinter party, Jul, contributed the Yule log. These enormously popular celebrations broke the Northern European cold and darkness with food and fire, marked the lengthening of days, and affirmed life in a lifeless season. Small wonder, then, that Christians would find such celebrations resonant.

But the early church did not celebrate Jesus’ birth. The sketchy, conflicting nativity accounts in scripture may reflect that ambivalence. Only after hundreds of years did the church appropriate and baptize those midwinter festivals, and it did so at a high and lasting cost. The historian Stephen Nissenbaum has said:

From the beginning, the Church’s hold over Christmas was (and remains still) rather tenuous. There were always people for whom Christmas was a time of pious devotion rather than carnival, but such people were always in the minority. It may not be going too far to say that Christmas has always been an extremely difficult holiday to Christianize.

Take St. Nicholas. Here’s a fourth-century saint about whom we know next to nothing, so his shoulders can carry multiple legends. And not only legends—he also bears many names, including Kris Kringle. Originally the German Christkindl meant Christ child; in corrupted form, now it is simply another name for Santa Claus. Just about as far back as the traditions go, there have been complaints that this magical figure has taken the place of Jesus. Sure enough, it’s a lot easier to accept a jolly man as the judge of who’s naughty and nice.

For a time, the wild parties ended. Recognizing that they could not keep rum out of the eggnog, 17th-century English Puritans tried to kill Christmas entirely, and they largely succeeded. Laws kept shops open on December 25; Parliament pointedly met on that date; newspapers mentioned almost no holiday activity. In Plymouth Colony, William Bradford made keeping Christmas a criminal offense.

It wasn’t until the 19th century, thanks in part to Charles Dickens, that Christmas came back into vogue. Widely published photographs of Queen Victoria and her German-born consort, Prince Albert, inspired the English and Americans to take up a German custom, the Christmas tree.

And since then, it has all been downhill. In Forbes’s felicitous image, Christmas has been a snowball, picking up size and detritus as it has rolled along. Clement C. Moore’s famous poem “The Night Before Christmas,” Thomas Nast’s illustrations, movies, songs, even seasonal advertisements for Coca-Cola have lent a timeless glow to a fairly recent, and fairly commercial, invention. In other words, a pure Christmas never existed.

It’s important to remember this whenever a cry goes up that Christ isn’t being kept in Christmas. Forbes, a professor of religion at Morningside College and a United Methodist, mildly comments:

One idea I do not recommend is a campaign to turn Christmas into the purely spiritual holiday it never was. My understanding is that the Christmas message is “incarnation,” that God entered fully into the world. So combining Jesus’ birthday party with at least some worldly celebrating seems appropriate.

It can look like the secular has triumphed over the sacred if you believe in such distinctions. In Japan, for example, millions of people enjoy a very American Christmas entirely divested of religious content. Evangelicals may call for abolishing the holiday altogether if it can’t be purified, but Forbes has an older and better idea: keep all 12 days of Christmas. By December 26, he says, the rest of the world has moved on; Christians have the days before Epiphany to themselves. He also begs us to be mindful of how Christmas affects others in a multicultural world. Some of his most poignant stories are about how Jews deal with holiday hegemony.

Forbes has written this little book for a general audience. It breaks no new ground, and he scrupulously avoids making definitive judgments, instead providing a survey of scholarship and conjecture. In his last and strongest chapter, he steps forward to share his own beliefs, which bring us back to his first words: he loves Christmas. With all its faults, he finds the holiday reassuring and inspiring.

Despite the commerce and frivolity, no one can miss the message of Christmas entirely. Somehow the incarnation keeps asserting itself; a religious tale gets told.