It comes up every three years, and every six years it coincides with a presidential or state election. I'm referring to this Sunday's Gospel passage, Matthew 22: 15-21, in which Jesus taught us to "repay to Caesar what belongs to Caesar and to God what belongs to God," and thereby established the principle of separation of church and state.

Only he didn't.

I have found, over the years, that making sense of the interplay between religious faith and civil duties is just about the hardest task before us. I feel fortunate to have learned of and read recently the book Separation of Church and State (2002) by Philip Hamburger.

This scholarly and methodical book gives a historical survey of the concerns of Americans as we formed a nation and dramatized our anxieties about personal freedom and possible encroachment upon said freedom. If we find that talking lucidly about these matters is difficult, the confusion is largely attributable to the "separation" concept itself.

We know that the "separation" terminology is not found in the First Amendment of the U.S. Constitution. Instead a subtle dance goes on between its two parts: the non-establishment-of-religion clause and the free-exercise-of-religion clause. The image of a "wall of separation" between church and state originates in an 1802 letter of President Thomas Jefferson to a Baptist group in Connecticut.

It seems that, during the 19th century, this image from Jefferson came to be used in a way which was decidedly hostile to "foreign" (that is, Catholic) religious adherents. Indeed, with regard to the functioning of public schools, numerous Protestant Christians sought to have things both ways. They felt they could forbid Catholic influence in schools while allowing the use of the Bible. The pretext: that Catholicism was an established religious body, while Protestantism in its various forms represented the beliefs of individuals.

One revelation for me was that, while I was aware of "nativist" (anti-foreign) movements of the mid-nineteenth century, I had no idea that, later in that century, there were numerous "secularist" movements comparable to today's militant atheism. Another revelation: that in the 20th century, the influence of the Ku Klux Klan could be felt in the highest court of the land. Hamburger's historical survey ends in 1947, when the language of Jefferson's 1802 letter is at last written into a U.S. Supreme Court decision.

Our national conversation on these matters has become decidedly muddled, and much credit for the confusion may be given to the concept of "separation." Whereas, in our nation's beginnings, it was expected that the values of religious believers would provide a salutary influence upon affairs of state, "separation" has turned into a sort of "quarantine" aimed at protecting the state from religious "infection."

Jesus did not speak of God and Caesar as if they could be looked upon as equivalent and operating in separate spheres. Jesus used the coin with Caesar's image to make the point that the concerns of Caesar are a paltry thing when contrasted with God as the author of all being and all life. Our hearts do not have separate "church" and "state" compartments. Each human being is to live with integrity. A believer's conviction about what is right for human society may well originate in his or her religious sensibility; this conviction, then, is a legitimate gift to society, not a threat against it.