On Sept. 22, 1862, Abraham Lincoln gathered his cabinet to tell them he was going to issue the Emancipation Proclamation. He said he had made a solemn vow to the Almighty that if God gave him victory at Antietam, Lincoln would issue the decree.

Lincoln's colleagues were stunned. They were not used to his basing policy on promises made to the Lord. They asked him to repeat what he'd just said. Lincoln conceded that "this might seem strange," but "God had decided the question in favor of the slaves."

I like to think about this episode when I hear militant secularists argue that faith should be kept out of politics. Like Martin Luther King Jr. a century later, Lincoln seemed to understand that epochal decisions are rarely made in a secular frame of mind. When great leaders make daring leaps, they often feel themselves surrendering to Divine Providence, and their strength flows from their faith that they are acting in accordance with transcendent moral truth.

And I also think back on Lincoln at moments like these, when other boundaries between church and state are a matter of hot dispute. Lincoln is apt, because this emancipation moment was actually exceptional. Lincoln was neither a scoffer nor a guy who could talk directly to God. Instead, he wrestled with faith, longing to be more religious, but never getting there.

Today, a lot of us are stuck in Lincoln's land. We reject the bland relativism of the militant secularists. We reject the smug ignorance of, say, a Robert Kuttner, who recently argued that the culture war is a contest between enlightened reason and dogmatic absolutism. But neither can we share the conviction of the orthodox believers, like the new pope, who find maximum freedom in obedience to eternal truth. We're a little nervous about the perfectionism that often infects evangelical politics, the rush to crash through procedural checks and balances in order to reach the point of maximum moral correctness.

Those of us stuck here in this wrestling-with-faith world find Lincoln to be our guide and navigator. Lincoln had enough firm conviction to lead a great moral crusade, but his zeal was tempered by doubt, and his governing style was dispassionate.

The key to Lincoln's approach is that he was mesmerized by religion, but could never shake his skepticism. Politically, he knew that the country needed the evangelicals' moral rigor to counteract the forces of selfishness and subjectivism, but he could never actually be an evangelical himself.

So, like many other Whigs, he was with the evangelicals, but not of them. This Whig-evangelical alliance was responsible for a great wave of internal improvements that transformed the country. Some of the improvements were material: the canals, the railroads. Some were spiritual: the Sunday school movement, the temperance movement. Some, like abolitionism, were both.

But as Daniel Walker Howe has noted, these efforts were all seen as part of the same reform agenda: to create a country of laboring, self-disciplined, upwardly striving (spiritually and materially) individuals.

Lincoln believed in this cause as fervently as anybody, but he was always trying to slow down his evangelical allies. As the great historian Allen C. Guelzo argues, Lincoln favored the classical virtue of prudence, which aims at incremental progress and, to borrow a phrase from Lincoln, at making sure that politics doesn't degenerate "into a violent and remorseless revolutionary struggle."

Lincoln came to believe in a God who was active in human affairs but who concealed himself. The only truths he could rely upon were those contained in the Declaration of Independence: that human beings are endowed with unalienable rights. We Americans can be ardent in championing that creed, but beyond that, it's best to be humble and cautious.

One lesson we can learn from Lincoln is that there is no one vocabulary we can use to settle great issues. There is the secular vocabulary and the sacred vocabulary. Whether the A.C.L.U. likes it or not, both are legitimate parts of the discussion.

Another is that while the evangelical tradition is deeply consistent with the American creed, sometimes evangelical causes can overflow the banks defined by our founding documents. I believe the social conservatives' attempt to end the judicial filibuster is one of these cases.

Lincoln's core lesson is that while the faithful and the faithless go at each other in their symbiotic culture war, those of us trapped wrestling with faith are not without the means to get up and lead.