In an earlier column, I promised to discuss why I believe children should generally be exempt from courses of instruction in the public schools when the parents find the material objectionable on religious grounds. This is a controversial claim, and few educators, and even fewer courts, are likely to buy it. But the rationale is simple: when the state forces children to learn material that the parents find religiously offensive, it is, in nearly all cases, violating the separation of church and state.

Yes, that's right: the separation of church and state. That hoary and much-overused American tradition that has become, unfortunately, a tool for restricting the freedom of religion needs at last to be returned to its roots—as a tool for restricting government interference with the freedom of religion.

Although the "separation" that everyone talks about is nowhere mentioned in the Constitution, the principle was widely understood well before the framing of the First Amendment. But the way it was understood is very different from the casual use one hears today.

The idea that church and state should be separated is firmly grounded in Protestant theology. But the splitting of these two great institutions was only that—a splitting of institutions. Both were expected to continue to live under the rule of the one God.

For example, when Puritan New England banned clergy from officiating at marriages, authorities were certainly not suggesting that marriage should no longer be governed by God's rules. Rather, the goal was to avoid church corruption. The Puritans were reacting to the Church of England's role in ceremonies they believed the Bible did not specifically entrust to the ministry.

And when Roger Williams penned what seems to be ...