[NB: This is a re-re-repost of a post that originally appeared here in 2009.]
Very often you'll hear some wiseacre deconstruct Christmas. He'll talk about its components—the date of Jesus' birth, the elements involved in Christmas celebration, etc.—then claim that Christmas is a sham in both form and content: no element of Christmas is originally Christian, after all. What usually follows, after this scholarly lecture, is the non sequitur that "the Christmas tree therefore isn't a Christian symbol."
Well, no: the tree is a Christian symbol because Christians have made it so. Christians who use Christmas trees aren't focusing on the tree's pagan, pre-Christian origins when they set such trees up. Celebrants of Christmas belong to a tradition that has appropriated the tree, i.e., made the tree its own.
Some people have a hard time wrapping their minds around the concept of appropriation, which isn't the same as the concept of theft (another idea associated, often rightly, with Christianity's frequently unhappy history). Here's a general example of how appropriation works: as Buddhism moved out of India and into other Asian countries, it took on the trappings of those countries. In Korean Buddhist temples, you might see imagery that's not originally Buddhist: mountain spirits, deities of magico-religious Taoism, etc., might all make their appearances somewhere on Buddhist ground. Buddhism appropriated the local colors and flavors, and was changed thereby. This is a natural sociological process, and it's not limited to religion: it happens in other human spheres as well—culture, politics, art, and all the other human endeavors you can think of. Ideas are memes; they cross-pollinate.
A more specific example: the bodhisattva Avalokiteshvara represents the sort of change that occurs as religions move from place to place. As the Indian name implies with the ending "-ishvara," this entity was a "lord," i.e., male. As the concept of Avalokiteshvara moved northward into China, however, it became associated with the Chinese deity Kwan Shih Yin (or just Kwan Yin)—a deity that was arguably native to China, and usually portrayed as female. Whatever Avalokiteshvara was, the Bodhisattva of Compassion is now thought of as female in all of East Asia. More philosophically minded Buddhists, aware of the bodhisattva's Indian origins, will say the bodhisattva transcends gender, but folkloric Buddhists in East Asia will be comfortable with Kwan Yin's femininity. East Asians appropriated Avalokiteshvara.
People who claim "X is not really X because it was originally Y" are demonstrating a lack of understanding about how symbols work. Culturally speaking, symbols derive their power and significance from a widespread agreement as to their general meaning. This agreement is often induced and enforced diachronically, when the older generation teaches the symbol's meaning to the younger generation.
It may sound strange to give so much legitimacy to the "because we said so" crowd, but the saying-so is integral to what symbols are. The implication, then, is that the critic of Christianity can't afford to be too smug about the "original" significance of the Christmas tree. Those pagans came to an agreement about what their tree meant, after all, and they may have done it in consonance with—or in defiance of—some even earlier, pre-pagan tradition.
If religious symbols are too abstract for you, let's think about this problem in terms of language. The sound "ah" occurs in American English, but it's also an ancient sound—one of three sounds common to all languages (the other two being "ee" and "ooh"). Does the ancient pedigree of "ah" make it somehow un-English? To put matters another way: "ah" might have come from our distant past, and might currently be found in other languages, but does that make it any less a part of English phonetics? Conclusion: "ah" is English—not originally English, nor exclusively English, but legitimately English all the same. And why? Because users of English have, through a massive and self-perpetuating agreement, chosen to include the sound as part of their language.*
By the same token, then, the tree known by Christians as "the Christmas tree" is certainly not exclusively Christian, nor is it originally Christian, but it is nonethless legitimately Christian. Why? Because Christians have made it so.
There's another side to this issue, though: we should take a moment to consider the Christians who get upset upon hearing that their precious symbol doesn't originate with their tradition. My question to them would be: why are you upset? Did you really think Christianity wasn't composed of non-Christian elements? As Thich Nhat Hanh notes in his Living Buddha, Living Christ, all religious traditions are composed of elements not of that tradition. Viewed in terms of Buddhist metaphysics, religious traditions are dependently co-arisen: they form out of a matrix of intercausality. The late Father Cenkner, one of my mentors at Catholic University, used to say: "It's all syncretism!"**
I personally have no trouble with the claim that the Christmas tree isn't originally Christian, or that prayer pre-dates Christianity, or that Madonna-and-Child imagery is very likely derived from Isis-and-Horus iconography, or that sacred birth narratives and the concept of resurrection are pre-Christian. None of this changes the fact that almost all Christians pray, that many Christians set up Christmas trees for Christian purposes at Christmas, or that the Madonna and Child are wholly integral to the Christian tradition. A healthy Christian attitude would be to realize that one is part of a constantly evolving and interwoven global network of tradition-streams. In the meantime, the non-Christian who attempts to claim that "aspect X of Christianity isn't originally Christian" needs to realize that this in no way implies that "aspect X isn't Christian"—a claim that is demonstrably false.
*Some scholars have proposed a "language model" of religious pluralism that makes religious traditions analogous to languages. The model is helpful in elucidating certain aspects of how religions may have evolved over time, but I question the model's effectiveness in resolving what many pluralists see as the basic problem of religious diversity—namely, the fact that the various traditions, in their doctrines and metaphysics, often make conflicting or even contradictory truth claims. If the language model is meant to be used normatively, it implies that no one religion is any more legitimate than another—an implication rejected not only by divergent pluralists but also by inclusivists and exclusivists. Even convergent pluralists exclude certain traditions from the sphere of legitimacy; Satanism, for example, immediately comes to mind.
**You're allowed to make sweeping generalizations about the universe when you're over 70, even if you're an academic. In his defense, I'll note that Father Cenkner said this outside of the class context. While the sentiment lacks the usual scholarly hedges and qualifications, I still think it's basically correct when applied to religion. Can you name a causa sui religious tradition?