To commemorate the end of a bloody Revolutionary War, George Washington issued what might be considered the first executive order, setting aside the last Thursday of November as a day of thanksgiving and prayer. His 1789 Thanksgiving Proclamation was short, a mere 456 words, punctuated by references—“Almighty God,” “the Lord and Ruler of Nations,” “the great and glorious Being,” “the beneficent Author of all the good that was, that is, or that will be”—to a Supreme Being.

Pointing to sources like the proclamation, today’s religious leaders often count Washington as one of their own. The late evangelical writer Tim LaHaye, whose Left Behind series sold over 11 million copies, cast Washington as a “devout believer in Jesus Christ” who had “accepted Him as His Lord and Savior.” David Barton, founder of WallBuilders, an evangelical Christian advocacy organization, and the former vice chairman of Texas’s Republican Party, pictured a reverent Washington kneeling in prayer at Valley Forge on the cover of his book, America’s Godly Heritage. And many politicians look to texts like Washington’s proclamation as proof that America was founded as a Christian nation.

But what did Washington’s talk of this “glorious Being” really mean at the time? Are these references proof that Washington would, in LaHaye’s words, “freely identify with the Bible-believing branch of evangelical Christianity?” Or do they mean something else—something that would have been clear to Washington’s audience in 1789—but which eludes us today?

To find out, research psychologist Eli Gottlieb and I conducted a study in which we asked people with varied levels of historical knowledge and religious commitment to read Washington’s proclamation and tell us what they thought. At one end of the spectrum were members of the clergy; at the other were agnostic and atheist scientists. We also questioned professional historians, religious and nonreligious alike.

Clergy and scientists agreed that Washington was deeply pious, but where they parted ways was about whether his piety should be applauded—or denounced. A Methodist minister found support in Washington for the claim that the United States was founded on a “general Christian faith” and that “religion and spirituality played a significant role” in American life, more so than people are willing to admit today.

For their part, scientists chaffed at Washington’s “violation of church and state.” A biologist compared the president to a “country preacher” who arrogantly assumed “that everybody believed the same thing.”

And the historians? They reacted so differently that it seemed as if they had read a different document entirely.

Regardless of their religious leanings, historians focused less on what was in Washington’s address than on what wasn’t. One historian remarked that the proclamation would “depress Pat Robertson,” the evangelical media mogul and chairman of TV’s Christian Broadcasting Network, who would fume at the fact that the proclamation made “no mention of Jesus Christ.” In lieu of recognizable markers of Christian piety—Jesus, Son of God, the cross, the blood of salvation, the Trinity, eternal life, the Resurrection—one finds airy and nondescript abstractions like “great and glorious Being” or “the Lord and Ruler of Nations.”

Historians were not deaf to Washington’s religious references. While the clergy and the scientists saw them as evidence of Washington’s devotion, the historians stressed the president’s precision in crafting a vocabulary that would unite the dizzying array of Protestant denominations in post-revolutionary America without alienating the small but important groups of Catholics, Jews, and freethinkers dotting the American landscape. It was precisely because he understood that Americans did not believe the same thing that Washington was scrupulous in choosing words that would be acceptable to a wide spectrum of religious groups.