In spite of that, feelings can sometimes run high over the question of caffeinated drinks, though they don't usually. Perhaps that is because the differences in practice are mostly regional. There are parts of the world in which most Mormons believe that they ought not to drink any caffeinated drinks.

But in other parts of the world, members of the LDS Church drink caffeinated drinks without a thought. In places like that a running joke is that the difference between Mormons and others is the temperature of their caffeine.

However, when Mormons from different subcultures get together, as they do at BYU, the differences become obvious and can sometimes result in irritated disagreement. Because avoidance of alcohol, tobacco, coffee, and tea have been obligatory for Mormons since the early 20th century, for many the question of whether to drink caffeinated drinks is really a question about one's relationship to the Church.

Those who don't drink them may sometimes see those who do as less faithful; those who do drink them may see those who don't as self-righteous. When the otherwise trivial question of caffeine becomes a question about faithfulness or self-righteousness, feelings can get irritable.

But the Word of Wisdom is about much more than whether I can or should drink a Diet Dr. Pepper with my lunch. As I see it, it is even about more than having a unique health code, though the health benefits of following the advice of the revelation are borne out by the average lower cancer rates, longer longevity, and generally better health of Mormons.

Perhaps the first thing that the revelation does is imbue the ordinary with the spiritual. That some foods are forbidden by God draws our attention to the fact that the rest are blessed by him for our nourishment and pleasure. Like saying a prayer of thanks over my meals, the Word of Wisdom reveals the sacred aspect in ordinary things. It is a more-or-less constant reminder.

The language of the revelation is a clue that it is more than a law about physical health. Its promise quotes Proverbs 3:8: "It [the fear of God] shall be health to thy navel, and marrow to thy bones." And the promise of physical vigor is a quotation from Isaiah 40:31: "They [those who serve the Lord] shall run, and not be weary; and they shall walk, and not faint."

The revelation borrows language from biblical texts in which promises of health are made, but not for eating this or that or refraining from eating. Rather the blessings are promised for fearing and serving the Lord. Using the Hebrew Bible's language, the revelation implicitly links obedience to its recommendations with showing respect for God and with serving him. To live the Word of Wisdom is to mark myself as having a particular relationship with God. Beyond its benefits to physical health, the Word of Wisdom serves as a sign of who I am.

That marking occurs in any number of ways. Every adult Mormon has had the experience of being with colleagues and turning down a glass of wine or a cup of coffee. Most of us don't say, "No thanks, Mormons don't drink coffee" since "No thanks" is enough. Not every friendly offer of a drink is an invitation for proselytizing. Nevertheless, even if we don't offer an explanation of our refusal, it isn't unusual for someone to ask for one. If I follow the Word of Wisdom, I cannot escape saying who I am whether explicitly or implicitly.

But even if no one asks about my beverage choice, in the moment when I'm asked and I say no, I am reminded of who I am. The Word of Wisdom marks me both to others and to myself.

As a result, living according to the Word of Wisdom also places me in a community. Turning down a cup of coffee reminds me that this is something we do.

Seeing someone else at a conference avoiding the coffee and tea, I'm almost certain to wonder whether she is also LDS. Refusing the invitation to have a glass of wine immediately identifies me to those who know another Mormon as a person like that other person.

The Word of Wisdom also serves as a constant reminder of what it means to be who I am. Refraining from a cup of coffee or tea or a glass of wine is a small sacrifice, but it is a sacrifice. Observing the Word of Wisdom means making a small sacrifice regularly, a token of my willingness to sacrifice more.

That token reminds me of what is expected and renews my covenant to meet that expectation: I am expected to fear God; I am expected to serve him. I am willing to do so.

My bodily health is at issue when I live by what the Word of Wisdom teaches, but more than that, my communal and spiritual health is at issue. The revelation reveals my identity as a Mormon with other Mormons, and it reveals the divine status of the world in which I find myself.

Beyond those, however, it reveals what I love and that I am willing to sacrifice for what I love. And it is not only an outward sign of those things. For whatever my obedience to the Word of Wisdom reveals to others, it mostly reveals to me who I am.