May 1 is the National Day of Prayer, created in 1952 by a Joint Resolution from Congress and the signature of President Harry Truman. It is a day, according to the website promoting it, that “represents a Judeo Christian expression of the national observance, based on our understanding that this country was birthed in prayer and in reverence for the God of the Bible.” And it is a bad idea.

National Days of Prayer have been around for a long time. George Washington had them. So did John Adams. But our third president refused to hold them, and his refusal gave us one of the most famous phrases in American history — “a strict wall of separation between Church and State.” Jefferson used this phrase in a letter to a group of Baptists written on the first day of 1802.Ostensibly, Jefferson wrote these words in a letter to the Danbury Baptist Association, a conservative evangelical group in Connecticut that strongly supported the strict separation of Church and State. Specifically, they supported the strict separation of the Congregational Church and the State of Connecticut. In 1802, states were still able to have established, tax-supported churches, and the Danbury Baptists, like nearly every other non-Congregationalist in New England, saw religion as a private affair between human beings and their God.

But Jefferson wasn’t really writing to the Danbury Baptists. He chose their letter out of thousands of congratulatory letters he received when he was elected president because it gave him a platform to respond to an issue that was quickly becoming a political controversy; namely, his refusal to proclaim “days of fasting and thanksgiving” for special events, as both George Washington and John Adams had done before him. This refusal played into the 1800 campaign narrative that Jefferson was an atheist, and he needed a quick way to nip the entire issue in the bud.

Jefferson’s response was brilliant — and typically Jeffersonian: he selected a congratulatory letter that he had received from a conservative religious organization and wrote an open response, to be published in New England newspapers indicating that he agreed completely with their position, that he saw the strict separation of Church and State as a key element of the Constitution, and that this belief prevented him from calling for government-sponsored days of fasting, prayer, and thanksgiving.

The first draft of the letter that Jefferson wrote to the Danbury Baptists reads, in part, as follows:

I have refrained from prescribing even those occasional performances of devotion, practiced indeed by the Executive of another nation as the legal head of its church, but subject here, as religious exercises only to the voluntary regulations and discipline of each respective sect.

In the final draft, at the suggestion of his secretary Levi Lincoln, Jefferson removed the last sentence and allowed the issue of “National Days of Fasting and Thanksgiving” to float in the background, thus giving us the version that we have today.Too often, people on both sides of the Church-State divide use Jefferson’s words as proof-texts for their own opinions instead of trying to understand what he meant. Jefferson was not anti-religious. His personal religious views (like those of many people) were murky, and often inconsistent, but his commitment to the separation of Church and State never wavered.

For Jefferson, the separation doctrine was not about protecting the Church from the State, or the State from the Church — it was about creating a genuine free market for religious ideas. This was the guiding vision of the “Virginia Statute for Religious Freedom" that Jefferson wrote in 1777.

“Truth is great, and will prevail if left to herself,” he wrote. And it has “nothing to fear from the conflict, unless by human interposition disarmed of her natural weapons free argument and debate.”

This is why Jefferson refused to declare Days of Prayer and Fasting. And it is why I believe that tomorrow’s festivities are ill-advised in a secular republic. A day of government-sponsored worship does not establish a theocracy or disenfranchise non-believers — just as a government “Day of Pepsi and Dr. Pepper” would not mean that somebody could not drink Coke. But it does put the government’s thumb on a scale where it does not belong — weighing in on the value of some beliefs over others.

And that is no way to run a free market.