Not quite, but Lincoln seems to have flirted with Deism, entertained evolution, and had a decidedly ambivalent, sometimes even hostile, relationship to conservative Christian religion. Lincoln biographer Richard Lawrence Miller, writing in Free Inquiry earlier this year, says the following:
For an isolated thinker whose acquaintance with religion was mainly through frontier preachers, the works by Volney and Paine may have opened new vistas. Billy Herndon said that after Lincoln began his Springfield residence in 1837, “He became acquainted with various men of his own way of thinking. At that time they called themselves free thinkers.” Matheny, one of Lincoln’s early Springfield friends, recalled Bible discussions among members of a Springfield poetry club. Lincoln “would bring the Bible with him, read a chapter, argue against it. . . . Lincoln was enthusiastic in his infidelity. As he grew older he grew more discreet, didn’t talk much before strangers about religion. But to friends—close and bosom ones—he was always open and avowed.” Matheny said he “heard Lincoln call Christ a bastard.”
And Lincoln was an early enthusiast for a popular book on evolution (written a couple of decades prior to Darwin’s Origin of Species ):
According to Billy Herndon, Lincoln admired a book called The Vestiges of Creation by Robert Chambers, which Lincoln read in the 1840s. This book argues that geological and biological evolution have occurred, that the earth is the product of a gaseous nebula, that life first occurred through a natural process, and that present creatures evolved from previous ones, all by processes dictated by scientific principles and laws. That book didn’t deny the existence of God but took a deist approach, saying, “To a reasonable mind the Divine attributes must appear, not diminished or reduced in some way, by supposing a creation by law, but infinitely exalted.”
Late in life, Lincoln appears to have become devout, though it’s not clear whether it was in the Orthodox sense, or whether he had merely adopted an intense and eccentric spirituality unique to his own person:
His best friend, Joshua Speed, related an incident from 1864, when Speed encountered Lincoln reading a Bible. “‘Well,’ said I, ‘if you have recovered from your skepticism, I am sorry to say that I have not.’ Looking me earnestly in the face, and placing his hand on my shoulder, he said: ‘You are wrong, Speed. Take all of this book upon reason that you can, and the balance on faith, and you will live and die a happier and better man.’” What converted Lincoln is difficult to know. His old friend Jo Gillespie said, “After he became President he told me that circumstances had happened during the war to induce him to a belief in ‘special providences.’” There are accounts of him engaging in intense prayer, and he told his cabinet that he issued the Emancipation Proclamation in fulfillment of a promise he made to God.
Miller sums up the older Lincoln’s religiosity this way:
Perhaps he found . . . reassurance in religion. If so, however, it was a big change in his life that was unnoticed by the person closest to him. After his death, his widow, Mary, said, “Mr. Lincoln had no hope—and no faith in the usual acceptation of those word[s].”
Abraham Lincoln, that great American Sphinx, seems to have taken the secrets of the exact nature of his deepest religious (and irreligious) beliefs to the grave with him. Perhaps, as a thoughtful and conflicted man, he could not articulate them consistently even to himself. Might the best word for such a man—the word that characterizes Lincoln’s life as a whole—be agnostic ?