His theory of governmental forgiveness was as irreconcilable with his theory of military discipline as his theory of divine mercy was with his system of inexorable law. He did not harmonize the contradictions: he was merciful, and let his system take the consequences, and he believed in a divine mercy while holding a theory with which the exercise of mercy was irreconcilable.
To such a mind as that of Abraham Lincoln, it was not necessary to prove the fact of immortality. If God possessed immortality and intended it for man, then God would make His decree effective in man. Adam's fall could not hopelessly lose to man what God designed; and, whether he accepted for himself or not the theory of the fall and of redemption, he accepted both in meeting an argument which by reason of the fall could have deprived man of his birthright of immortality. He believed in the immortality of the soul.
Did he harmonize that doctrine with the rest of his creed? Probably not. He was no theologian, in the strict and formal sense, no logician. He reasoned on the basis of very simple and elementary principles, whose lines of direction were determined by the early Calvinistic preaching to which he listened, the rationalistic method which he learned from Paine, and his simple sense of justice and right.
His was not wholly an optimistic faith. He knew that man was sinful and sad and that "the spirit of mortal" had little occasion for pride; but he believed in an eternal justice and an unconquerable goodness, regnant above the perplexities and contradictions of this life, and triumphant in the life everlasting.
Abraham Lincoln believed in God. Save in his moments of deepest gloom when everything turned black, he appears never seriously to have questioned this fundamental article of belief. It is not easy to see how he could have done so. His idea of causation forbade it, and, what was more, his profound supernaturalism affirmed it as incontrovertible. This element of supernaturalism went the full length of orthodox preaching, as Lincoln heard it and accepted it. It was in accord with the teachings both of the Baptists, whom he heard in Indiana and rural Illinois, and the Presbyterians, to whom he listened in Springfield and in Washington. In a great God, a mighty Creator, a Sovereign Ruler, he was taught to believe by all the forms of Calvinism to which throughout his life he listened, and it was in full essential accord with his own native tendency. His supernaturalism was not only ultra-orthodox; it went the full length of current superstition. The frontiersman of that day had superstition wrought into him by the vastness of the wilderness, the solemnity of the immeasurable forest and plain, and the insignificance of man; the haunting tales of savagery and witchcraft; the presence in every frontier community of some person supposed to be possessed of second sight or other supernatural qualities. The rationalism of his mature years modified but did not in any degree eradicate his supernaturalism.