It is easy to forget how odd some of the things serious Christians say and do must seem to people who are not familiar with the faith. I suspect there are times when people think Christians must be from another planet. Maybe that is why St. Peter calls them “aliens.”

Take, for example, the instructions Jesus and the apostles give regarding sex. It can be summarized this way: faithfulness in marriage, celibacy outside marriage. To people who are unacquainted with Christian teaching, this seems crazy. As C. S. Lewis said long ago: “Chastity is the most unpopular of our Christian virtues.”

The biblical proscription against profanity and foul language is another example. Many people, including Christians, think: “They are just words, so how can they be immoral?” But the contempt, anger, and arrogance that lie behind such words are the opposite of the humble, loving life Christ desires for his people.

But it is not just the proscribed behaviors that seem odd to people; it is also the ones that are prescribed. For example, the Apostle Paul, in line with his upbringing in Judaism, calls on Christians to rejoice, and even to rejoice always.

This sounds like evidence of a mental illness to people who are outside the faith. For example, when people who do not have a grasp of Christianity’s big picture hear Paul say, “We rejoice in our sufferings,” or stumble onto St. James’s command to “consider it nothing but joy when you fall into all sorts of trials,” it seems like madness.

There are times when it seems like madness to Jesus’s followers too. I recently missed a speaking appointment, which never got put on my calendar. When I learned what had happened, I was ashamed and humiliated. Would Sts. Paul and James say that I should rejoice in that situation? Wouldn’t that be tantamount to saying that faithfulness to my word is unimportant?

Not at all. Following the biblical injunction to rejoice does not downplay our failures nor does it make light of our sorrows. If I lose my spouse, for example, and continue to “rejoice in the Lord,” it does not mean the loss was not grievous or my love was not sincere. It means that I have reason to believe that things will be okay, and better than okay—for my spouse, myself, and God’s creation.

This example of a seemingly odd Christian teaching is particularly helpful because it illustrates how the lifestyle instruction given to Christians makes sense within a Christian worldview. Outside that worldview, those same instructions seem unworkable or unreasonable.

I can rejoice always, as St. Paul instructed, because the good news of Jesus promises that death has been overcome and that God will make all things new. I can rejoice because a day is coming for me and for all of God’s people when there will be “no more death, or mourning, or crying, or pain.” I can rejoice because God is making me more than I could ever be on my own and he is doing it not despite my failures and sorrows but in the midst of them.

Christian lifestyle teaching, which seems odd or antiquated to people who do not understand the Christian way, is intended to help the follower of Jesus enjoy life and be helpful to others, which in turn brings glory to God. This is obviously true when it comes to Christian sexual ethics, where faithfulness to my wife makes her life better, our children’s lives better, and my life better. But it is also true of instructions like, “Rejoice always.”

That command comes on the coattails of an instruction to do “everything without grumbling or disputing.” How much more enjoyable a life without grumbling and disputes would be for those who follow this instruction—and for those around them. But that instruction is impossible to follow apart from obedience to the command to rejoice.

The various lifestyle instructions given to Christians are interlocking, like the pieces of a puzzle. When they are in place, they lend support to the whole and they form a picture – a compelling picture – of the beautiful life of faith in God.