When I was in junior high, a friend of my father would engage me in theological debate. Of course, I wasn't up to the task, but I consider it part of my training. I loved every minute of it.
"Why didn't you wear a head covering in church today, Heather?" he'd ask.
I'd stammer and stutter. I didn't know then about the cult prostitutes and the new Roman woman. But the one phrase that caught me said, "But if it is disgraceful for a woman to have her hair cut off or her head shaved, she should cover her head."
"It's not disgraceful today for a woman to have her hair cut off or her head shaved," I told him.
The debate continued on. I never "won" (nor did I ever wear a head covering to church), but even then, I sensed that there was something in the culture of Paul's day that was different from the culture of our day, and that changes how we do things sometimes.
Years later in seminary, a professor introduced me to the concept of form, function, and meaning. Every form has a specific function, and this function shows a certain meaning. If the function and meaning of the form are the same from one culture to the next--and I mean the broader culture, not our church subcultures--then by all means, keep the form. If it isn't, then the same form without the same function and meaning is meaningless at best and confusing at worst.
Take, for example, the holy kiss. Paul commands us to greet one another with a holy kiss. In his day, the holy kiss (the form) had a function of showing warmth, friendship, and hospitality. The command, then, meant to welcome fellow Christians into your home and church with warmth, friendship, and hospitality. It was a way of showing Jesus' command to love each other and be of one body (see John 17).
Today, if you came into my church for the first time, and I gave you a kiss on the lips (which is how it would have been practiced in Paul's church), you'd at best back slowly out of the church and at worst tell others about the weird cult you accidentally went to once. In our culture, a kiss on the lips hardly means friendship. But the command to welcome others into our churches and homes with love and hospitality still stands (and I've been to many churches who've forgotten this command). It means anything from something as simple as a handshake to asking a newcomer to lunch.
(By the way, there are other cultures--meaning broader cultures, not church subcultures--that practice a kiss, whether on the cheeks or on the lips, as a welcome of friendship.)
Going back to the head coverings, we can use the same ideas to evaluate whether or not women wearing head coverings is appropriate in our churches.
In Paul's day, it was shameful for women to shave their heads because that was a practice of cult prostitutes. In these early days of church establishment, outsiders mistook the church for the fertility cult. Paul warned women to cover their heads (form) to show that they were honorable women, not cult prostitutes, who went without head coverings or with shaved heads, and not contentious new Roman women, who were a type of extreme feminists of the day (function). In so doing, they would communicate that the church was not the fertility cult nor was it a contentious group (such as the new Roman women who were stirring up all sorts of trouble by publicly denouncing marriage and childbirth, claiming women were above men, and participating in the fertility cults) but were a peacable group that submitted to government authorities as much as possible (meaning).
In our culture--meaning the United States, not our local church subcultures--does wearing a head covering have the same function or communicate the same meaning? No, but the truth stands that we should communicate we are a peacable group that as much as possible submits to government authorities.
This tool of evaluation can also be helpful for issues not directly addressed in the bible (not because God didn't foresee them but because they weren't part of the stories and cultures of the day).
Take, for example, jack-o-lanterns. Can Christians participate in Halloween and display decorations such as jack-o-lanterns? I would argue that the answer is not the same for every Christian. The answer requires the Christian to understand her culture and be sensitive to what it means in her neighborhood. In most parts of the United States, a jack-o-lantern is harmless fun. It's a way of engaging the imagination in a game of pretend. It's function is nothing more than laughter, and its meaning can be a way of connecting and participating with your neighbors.
In a few places, though, a Christian may live in an area where witchcraft is prominent and by displaying things such as jack-o-lanterns and witches riding brooms, they connect themselves with different cults. (Again, the evaluation for the most part should be according to the larger culture, not church culture, which has a habit of artificially carrying cultural meanings.)
Let's look at one more example: Eucharist or communion. In the first century, it's form was the loaf of unleavened bread from the Passover feast and a glass of wine. It's function--a sign of the new covenant. It's meaning--to participate in the new covenant, to be nourished with spiritual food, and to remember and proclaim Christ's death and resurrection. The form took everyday items found on every table and infused them with spiritual meaning.
We continue the practice today, but we don't always use the same form. Some use grape juice. Or the bread we use may be wafers or crackers or a loaf of leavened bread. I even heard of one church using Doritos and Coca-Cola--everyday items they infused with a spiritual meaning. How far can we take this?
This type of thinking isn't an exact science. It gives us a guideline as we seek to understand how Christians reflected God in their culture and how we can reflect God in our culture.