As Christianity spread throughout the Greco-Roman world, it became apparent that the biblical doctrines concerning God, morality, and future retribution had similarities with the philosophical speculations of the Platonists, Aristotelians, and Stoics. The Fathers and medieval theologians had no difficulty in admitting this; on the contrary, they saw it as a confirmation of the truth of revelation. Human reason at its best, they explained, is able to discover some of the doctrines that God revealed through the prophets and Jesus Christ.

This being granted, revelation was still necessary for two reasons. First, because even the naturally knowable truths were attained only by a few, and by them with great difficulty and a considerable admixture of error. Second, because certain truths very important for salvation could not be attained in any other way than by revelation accepted in faith. Among the truths in this second category were the Trinity, the Incarnation, the redemptive death of Christ on the Cross, his Resurrection and Ascension into glory, the institution of the Church, the sacraments, the bestowal of grace, and the beatific vision. Human reason could find solid reasons for believing the Christian revelation, but in the end the believer had to make a free and trusting commitment to the word of God. In that sense, faith was above reason.

The position on faith and reason that I have just sketched is not simply that of ancient or medieval Christianity. It remains, by and large, the standard position held today, with varying nuances, by Catholics, Orthodox, Anglicans, and many Protestants. Revelation is relatively necessary to know religious truths that lie within the grasp of reason and is absolutely necessary to know strict mysteries.

In the seventeenth century an alternative position was put forward in England by Lord Herbert of Cherbury (1583-1648). He maintained that revelation was unnecessary because human reason was able to know all the truths requisite for salvation. In this list he included three primary truths: the existence of God, the moral law, and retribution in a future life. God, according to Lord Herbert, had implanted in the human soul from the beginning five innate religious ideas: the existence of God, divine worship, the practice of virtue, repentance for sin, and personal immortality.

Shortly after its invention by Lord Herbert, deism received indirect support from the physics of Isaac Newton (1642-1727) and the philosophy of John Locke (1632-1704). The physical world, according to Newton, was explicable in terms of “insurmountable and uniform natural laws” that could be discovered by observation and formulated mathematically. By mastering these laws human reason could explain cosmic events that had previously been ascribed to divine intervention. The beauty and variety of the system, Newton believed, was irrefutable evidence that it had been designed and produced by an intelligent and powerful Creator. Close though he was to deism, Newton differed from the strict deists insofar as he invoked God as a special physical cause to keep the planets in stable orbits. He believed in biblical prophecies, but rejected the doctrines of the Trinity and Incarnation as irrational.

Newton’s close friend John Locke, though not a deist, supplied an epistemological grounding for deism more plausible than the innatism of Lord Herbert. Beginning with human experience of the external world, he accepted a version of the argument from causality that demonstrated, as he thought, the existence of God as the uncaused Necessary Being, eternal, all-powerful, and all-knowing. Locke also believed in Christian revelation on the ground of biblical prophecies and miracles. But he held that reason should be the ultimate judge of all truth and that the firmness of our assent to any proposition should not exceed the strength of the evidence that we could produce in its favor. It followed that revealed truths, which rested on indirect proofs from reports in Scripture and tradition, were less certain than things known directly by reason. He rejected certain Christian doctrines such as the Trinity and the Incarnation, which in his judgment failed to meet the test of rational coherence. But, as I have said, he regarded himself as a Christian because he accepted Jesus Christ as the Messiah foretold in biblical prophecy; he had no difficulty in admitting the miracles ascribed in the Bible to the prophets and to Jesus.

From Locke’s system it was but a small step to deism. In 1696 his disciple John Toland published the book Christianity not Mysterious, in which he attributed the mysteries of Christianity to pagan conceptions and the machinations of priestcraft. In 1730 another disciple, Matthew Tindal, published the book Christianity as Old as Creation , in which he sought to demonstrate that all rational creatures have access to “a law of nature or reason, absolutely perfect, eternal, and unchangeable; and that the design of the gospel was not to add to, or take from this law,” but only to rescue humankind from superstition. Tindal’s work, more radical than Toland’s, came be used as a kind of Bible of deism. Both Toland and Tindal were Christian deists; they accepted revelation but maintained that it was nothing more than a republication of the religion of pure reason. Reason alone, they believed, could establish the fundamental truths necessary for salvation.

Three forms of deism may be distinguished, at least schematically. The first, most friendly to faith, admitted two channels of truth: reason, which gave access to the essential and necessary truths, and revelation, which communicated certain supplementary truths, useful but not essential for salvation. According to the second version, revelation was an aid to reason, but it could do no more than confirm or clarify truths accessible to reason alone. The most radical form held that reason was the sole font of truth and that revelation was nonexistent.

English deism spread rapidly to the continent, especially to France, where it was taken up by Voltaire, d’Alembert, and other Encyclopedists. Many of them tended to radicalize the system and use it as a weapon against revealed religion and especially against the Catholic Church.

The deist outlook also gained a foothold in the American colonies, where it became popular among the rich and well-born about the time of the Revolution. Of the fifty-six signers of the Declaration of Independence, the theological leanings of some twenty have been identified. Three have been characterized as deists: Benjamin Franklin of Pennsylvania, Thomas Jefferson of Virginia, and Stephen Hopkins of Rhode Island. Two others, John Adams of Massachusetts and George Wythe of Virginia, are described as liberal Christians strongly influenced by deism. Four, including Jefferson’s friend Benjamin Rush, were liberals not inclined toward deism. About eleven were definitely orthodox believers. Samuel Huntington, Philip Livingston, and John Witherspoon, president of Princeton University, were prominent in this last group.

Among the founders of the American republic who were not signers of the Declaration of Independence, George Washington, James Madison, and George Mason were religious liberals leaning toward deism. Samuel Adams, Patrick Henry, and Alexander Hamilton were generally orthodox Christians opposed to deism.

None of the Founding Fathers meditated more assiduously on religion than Thomas Jefferson (1743-1826). He was brought up in the rituals and traditions of the Anglican Church, as it existed in Virginia at the time. In his college years at William and Mary he came to admire Francis Bacon, Isaac Newton, and John Locke as three great paragons of wisdom. Under the influence of several professors he converted to the deist philosophy. He made a careful study of the philosophical writings of Viscount Henry Bolingbroke, a strict deist whose God was remote and unconcerned with human affairs.

In his public pronouncements as a statesman and legislator, Jefferson expressed what he considered to belong to the common and public core of religion. He kept his more personal opinions to himself, refraining from putting them in any writing that might find its way into print, but he occasionally penned confidential memoranda for himself and a few friends.

Jefferson’s public religion appears in the Declaration of Independence, which refers to “the laws of Nature and Nature’s God,” to “inalienable” rights conferred upon all human beings by their Creator, and to “the protection of divine Providence.” In his first inaugural address, in 1801, Jefferson spoke of how the American people were “enlightened by a benign religion, professed indeed, and practiced in various forms, yet all of them inculcating honesty, truth, temperance, gratitude, and love of man, acknowledging and adoring an overruling Providence.” In his second inaugural, four years later, he emphasized the nation’s need for the favor and enlightenment of Providence and asked his hearers to unite with him in supplication to “that Being in whose hands we are.”

One of Jefferson’s firmest principles, as we know, was that of religious freedom. In 1777, as a legislator, he composed what later became the Virginia Statute on Religious Freedom, which embodies his personal conviction that the government should exercise no coercion in religious matters. In his famous letter of 1802 to the Danbury Baptist Association he referred to the “wall of separation between Church and State” ” a term that had previously been used by the Baptist Roger Williams. But as we have seen, he did not hesitate to bring religion into his public pronouncements. As President he frequently attended religious services in Congress. While opposing a federal religious establishment, “he personally encouraged and symbolically supported religion by attending public church services in the Capitol,” as Daniel Driesbach has written.

Like his contemporaries Franklin, Washington, Adams, Hamilton, and Madison, Jefferson was convinced that the republic could not stand without a high level of public morality, and that moral behavior could not survive in the absence of divine authority as its sanction. Obedience to the teachings of Jesus and reflection on the purity of Jesus’ life could enable people to overcome their selfishness and parochialism.

Jefferson’s friend Joseph Priestley (1733-1804) maintained that the authentic teachings of Jesus were vastly superior to those of Socrates or any other pagan but that they had been overlaid by a thick cover of legend and mythology, which must be stripped away for the truth to shine forth in its pristine brilliance. Priestley’s work made a deep impression on Jefferson and enabled him to regard himself as a Christian. Following in Priestley’s footsteps, Jefferson undertook to retrieve the true teachings of Jesus, especially in matters of morals. To this end he made two compilations of texts concerning Jesus from the New Testament. The first, entitled The Philosophy of Jesus , was completed in 1804 but has been lost. The second, which he called The Life and Morals of Jesus , is usually known as the Jefferson Bible. It was composed in his later years and published only after his death. Omitting all references to the miraculous and the supernatural, Jefferson selected what he took to be authentic sayings of Jesus as a moral teacher. The precepts of the Nazarene, he asserted, were “the most pure, benevolent, and sublime which have ever been preached to man.” The religion of Jesus, he believed, was so simple that it could be understood by a child, but the writers of the New Testament, especially Paul, overlaid it with mythology derived from Platonist sources. The sage of Monticello forthrightly dismissed dogmas such as the Trinity and the Incarnation, which he found unintelligible.

Jefferson’s religion, however, was not purely philosophical. For a living religion, he knew, scope must be given to the inclinations of the heart. He was enraptured by the beauty of the Psalms, which in his opinion surpassed all the hymnists of every language and of every time, including the hymn of Cleanthes to Jupiter so much admired by his friend John Adams. When he attended church services as an old man, the sounds of familiar hymns would bring tears to his eyes.

In his plan of studies for the University of Virginia Jefferson wanted natural religion to be taught to the exclusion of all doctrine attributed to revelation. But he knew that religion could not be purely academic and therefore recognized the importance of worship in the churches. He took pride in the fact that students at his university had opportunities to worship in Episcopal, Presbyterian, Methodist, and Baptist services in the sanctuary at Charlottesville. Interdenominational competition, he believed, was the best protection against fanaticism. In matters of religion the aphorism “united we stand, divided we fall” had to be reversed. Divided we stand, he said, but united we fall.

In summary, then, Jefferson was a deist because he believed in one God, in divine providence, in the divine moral law, and in rewards and punishments after death, but did not believe in supernatural revelation. He was a Christian deist because he saw Christianity as the highest expression of natural religion and Jesus as an incomparably great moral teacher. He was not an orthodox Christian because he rejected, among other things, the doctrines that Jesus was the promised Messiah and the incarnate Son of God.

Jefferson’s religion is fairly typical of the American form of deism in his day. But a vocal minority of American deists were, like many of the French Encyclopedists, opposed to Christianity. Thomas Paine, the most famous of this group, was often accused of atheism, but he, like Voltaire, believed in God the Creator. Even radical deists like Paine agreed with Jefferson and Franklin that without belief in God and in a future life, morality in society could not be sustained.

In the closing decades of the eighteenth century, deism in the United States, as elsewhere, seemed to be sweeping everything before it. But early in the nineteenth century, the deist tide began to recede. The first half of the nineteenth century witnessed a significant revival of Christianity, both Protestant and Catholic. The preachers of the second Great Awakening were especially successful in rural America, where they aroused a highly emotional biblically based religion. While Unitarianism survived and even experienced some growth in New England, it lost its specifically deist features: the sharp dichotomy between faith and reason, the deductivist natural theology, the separation between God and the world, and the idea of Jesus as teacher of the natural law. Deism therefore may be said to have perished, not only in the United States but also in England, France, and Germany.

We can discern several reasons why deism, which once looked so promising, proved unable to sustain itself. Deism drew its vitality from the oppressive policies of the religious establishments against which it was reacting. In the minds of the Enlightenment thinkers, confessional religion, unless checked by law or by free competition, led inevitably to tyranny and persecution. But this assumption was based on a time-conditioned union or alliance between throne and altar, not on the gospel of Christ, which gave Caesar no authority over the things of God.

Jefferson himself came gradually to this realization. As a young adult he seems to have held that Christian faith was favorable to despotism and hostile to free society. But his friend Benjamin Rush convinced him that Christianity and republicanism were, so to speak, made for each other. As Eugene Sheridan has written, Rush regarded Christianity as “part of a divine plan to bring about the kingdom of God on earth by freeing mankind from the burden of royal and ecclesiastical oppression through the spread of the principles of human equality and Christian charity.” With Rush’s help Jefferson found a way of accepting Christianity without diminishing his commitment to the freedom of conscience. Deism, therefore, was not necessary to offset religious oppression.

By the middle of the twentieth century the major branches of Christianity accepted the principle of religious freedom not as a reluctant concession but as a requirement of the gospel itself. The Catholic Church in its “Declaration on Religious Freedom” ( Dignitatis Humanae ) teaches that the gospel itself demands that “in matters religious every manner of coercion on the part of men should be excluded.” A major factor in the rise of deism has therefore ceased to exist.

Although deism portrayed itself as a pure product of unaided reason, it was not what it claimed to be. Its basic tenets concerning God, the virtuous life, and rewards beyond the grave were in fact derived from Christianity, the faith in which the deists themselves had been reared. It is doubtful whether anyone who had not been brought up in a biblical religion could embrace the tenets of deism. The children of deists rarely persevered in the faith of their parents.

Deism also suffered from grave philosophical weaknesses. Its leading proponents were pamphleteers such as Toland and Tindal in England and Encyclopedists such as Diderot in France. They lacked the metaphysical principles needed to build a viable natural theology. Empiricists like Locke and rationalists like Newton lacked the rich ontology of Thomas Aquinas and the medieval schoolmen. Their epistemology was a shallow empiricism and their cosmology a universalized physics, both of which crumbled when faced with the penetrating critiques of David Hume and Immanuel Kant.

Additionally, the deist system suffered from some internal tensions. If there is an omnipotent God, capable of designing the entire universe and launching it into existence, it seems strange to hold that this God cannot intervene in the world He had made or derogate from the laws He had established. He might have good reasons for bestowing some added benefits not contained in the work of creation. American deists such as Jefferson and Franklin did not rule out all divine intervention. They were convinced that God punished evil and rewarded virtue both in this life and in the next. They also encouraged prayer in ways that seemed inconsistent with deism in its pure form.

If God was infinite in being, moreover, it was unreasonable to reject the notion of mystery. It would seem quite natural to suppose that there are depths of the divine being surpassing all that could be inferred from the created world. We cannot know what is going on in the minds of our fellow human beings unless they manifest it by word or deed. How much less, then, could we grasp the thoughts of God unless He were to disclose them to us by revelation? Since God knows far more about Himself and His plans than His creatures do, it is difficult to see why He could not reveal truths hidden from reason that would be important for persons such as ourselves. Throughout the centuries Christianity has held that central articles of faith, such as the Trinity, the Incarnation, and the atoning death of Christ, are revealed truths. We can understand them to some extent even if we cannot penetrate the full richness of their meaning.

Yet more, the deist God, who ceased to be active after launching the world into existence, seemed to be a useless vestige of the God of biblical religion. If God never intervened in the world, His existence could only be, from a human perspective, superfluous. It would be pointless to pray to Him or expect any blessings from Him. The pupils of the deists, carrying the critique of religion one stage further, questioned the existence of this idle Supreme Being. Thus deism came to be a halfway house on the road to atheism. Toland drifted gradually from deism into pantheism. Voltaire was unable to dissuade his erstwhile allies Diderot and d’Holbach from abandoning the deist camp and embracing atheism. In the United States atheism surfaced more slowly but was defended in the nineteenth century by Robert Ingersoll among others.

Yet another weakness in the deist system was the time-conditioned nature of its cosmological underpinnings. The system presupposed the static unalterable order of nature that appealed to mathematicians like Isaac Newton. But as the positive sciences matured, the universe appeared to be far less orderly than the deists had assumed. Eventually the Newtonian system would be superseded by the theories of Darwin and Huxley, Einstein and Heisenberg. William Paley’s depiction of God as the cosmic watchmaker lost its plausibility.

Deism also failed as a religion. Its static deity was a pallid reflection of the God of Abraham, Isaac, and Jesus Christ. The religion of the New Testament and of orthodox Christianity offered hope and consolation that lay far beyond the powers of deism. The gospel assures us that God never ceases to be active in the world: He freely calls us to Himself, hears our prayers, and enriches our lives with His grace. The doctrine that God became man in order to raise us to a share in His own divine life satisfied a deep desire of the human heart to which deism could not respond. It was impossible to enter into communion of life and love with the cold and distant God of deism.

Finally, the deist reconstruction of the historical Jesus lacked any serious foundation in biblical research. Jefferson claimed that it was “obvious and easy” to distinguish the authentic words of Jesus from those attributed to him by later Christians. In his view they were “as easily distinguishable as diamonds in a dunghill.” But even the most confident members of the Jesus Seminar today would make no such claim. Jefferson fell into the common error of simply projecting onto Jesus the moral ideals of his age.

An older contemporary of Jefferson, the German deist H. S. Reimarus (1694-1768), composed a lengthy Defense for the Rational Adorers of God , fragments of which were posthumously published by Gotthold Lessing in 1778. His fragment on “The True Aims of Jesus and His Disciples,” apparently unknown to Jefferson, was the first serious effort to reconstruct the life and preaching of Jesus with the tools of critical history. Although he was a deist himself, Reimarus did not attribute his own philosophy to Jesus. On the contrary, he regarded Jesus as a deluded apocalyptic preacher who shared the Jewish expectations of his day about the imminent arrival of the kingdom of God.

The long history of the quest for the historical Jesus that dates from Reimarus has overthrown the liberal humanitarian portrait. All the available sources point to a figure totally unlike the enlightened moral teacher postulated by Franklin and Jefferson. The teaching of Jesus, as reported in the earliest testimonies, is inextricably bound up with his messianic or divine claims and with the miraculous deeds by which he vindicated them. The belief and evangelizing fervor of the apostles cannot be accounted for without reference to the claims of Jesus, his miracles, and his bodily resurrection. Benjamin Rush pointed out to Jefferson his failure to address these objections, but Jefferson was unresponsive.

Because of these and other weaknesses, deism deserved to perish as it did, but it did not die without leaving a valuable legacy. Its influence on the American tradition has been enduring, beneficial and, one might say, providential. Although the Founding Fathers refrained from enshrining the particular theses of deism in official documents or public speeches, they composed these statements in such a way as to affirm the vestiges of faith that still survived in Christian deism without excluding more robust forms of Jewish and Christian faith.

Our American republic has therefore had what, following Jean-Jacques Rousseau, we may call a civil religion. Rousseau enumerates the positive dogmas of such a religion as follows: “the existence of a mighty, intelligent, beneficent divinity, possessed of foresight and providence, the life to come, the happiness of the just, the punishment of the wicked, and [Rousseau added] the sanctity of the social contract.” The civil religion of this country has been expressed in our national institutions and in the great pronouncements of our national heroes, most notably Abraham Lincoln.

The dominance of civil religion produced a favorable climate in which the various forms of biblical religion could and did thrive. Although the United States was never, in the technical sense, a Christian nation, it has been and remains a nation in which the biblical faiths are at home and in which other religions are welcome, provided that their tenets and practices are not a threat to public order. Deism by itself was too dry and abstract to elicit warm adherence, but the American consensus always surrounded the positive teachings of deism with the flesh and bones of specific faiths, whether Protestant, Catholic, or Jewish. The American civil religion can still be heard in the pronouncements of recent Presidents, but it is now being eroded or at least threatened by the increasingly pluralist shape of American society and by a judiciary that is reluctant to support or encourage any form of religion, however generic.

Today, therefore, we are faced with new questions. Can the biblical religions maintain themselves and win new adherents or must they resign themselves to becoming a minority? Should the American consensus be modified to make room for a broader pluralism? Can Islam, the Eastern religions, New Age religion, and even agnosticism and atheism, find equal acceptance in American society?

Jefferson would probably have insisted on the positive articles of deism as a required minimum. For him and the other Founding Fathers, the good of society requires a people who believe in one almighty God, in providence, in a divinely given moral code, in a future life, and in divinely administered rewards and punishments. He and they expected that the example and teachings of Jesus, as known from the Gospels, would be accepted in principle by the great majority of citizens. Although Jefferson wanted the state to refrain from meddling in the particulars of religion, he counted on families, churches, and educational institutions to perpetuate and disseminate in more vivid and concrete forms the basic truths also taught in his moderate form of deism.

If he were alive today, Jefferson would doubtless ask himself whether the welfare of the republic can stand in the absence of the minimal consensus I have described. If pluralism goes unchecked, will the nation still have a corporate vision sufficient to sustain the sense of mission and collective purpose that have characterized it at its best? Will factionalism, corruption, violence, and aimlessness proliferate? Each of us must strive to answer these questions as best we can with the help of the Sage of Monticello.

Avery Cardinal Dulles, S.J. holds the Laurence J. McGinley Chair in Religion and Society at Fordham University.