What Is Natural Theology?

What Is the Question?

Natural theology is the project of learning truths about God from reason and the natural world, without appeal to special revelation. Its contrast is with revealed theology, which learns truths about God from scripture, tradition, and the authoritative teaching of a religious community. The natural theologian works from what is available to any rational inquirer, the existence and order of the world, the fact of moral experience, the deliverances of religious experience, and tries to infer, by argument, what may be known about God.

The SEP entry on philosophy of religion treats natural theology as the central project of the discipline from its medieval origins through the early modern period, and as the contested core of the contemporary debate. The project depends on the assumption that human reason can reach truths about God without special revelation, an assumption that has been challenged from within theology by Karl Barth and from without by the Enlightenment critics. The question is what the project amounts to, what its main arguments are, and whether the arguments succeed.

Historical Background

The project is ancient. The Greek philosophers, especially Plato and Aristotle, argued from the order of the world to a divine cause. Augustine, in City of God and the Confessions, treated reason as a route to God, though he insisted that the deepest truths come through revelation and grace. Aquinas gave the project its classical form in the Summa Theologica, especially in the Five Ways, the five arguments for the existence of God. The Five Ways are: from motion to an unmoved mover; from causation to an uncaused cause; from contingency to a necessary being; from gradation of being to a maximum being; and from design to an intelligent designer.

The Five Ways are not, as they are sometimes caricatured, naive arguments from the existence of the world to the God of the Bible. They are careful metaphysical arguments, drawing on Aristotle and Neoplatonism, and they conclude to a divine cause that Aquinas then identifies, by further argument, with the God of Christian theology. The Five Ways are the model for natural theology, and the medieval tradition developed them in enormous detail, in the Summa Contra Gentiles and the commentaries on Aristotle.

The early modern period continued the project. Descartes gave the ontological argument its modern form, in the Fifth Meditation, arguing that the very concept of a supremely perfect being entails existence, because existence is a perfection. Leibniz, Spinoza, and Pascal all contributed to the project, and the natural theology of the seventeenth century was the shared framework of the European intellectual world.

Hume and Kant

The eighteenth century was the crisis of natural theology. David Hume, in the Dialogues Concerning Natural Religion, subjected the design argument to a devastating critique. Hume argued that the analogy between the world and a human artifact, such as a watch, is weak, because we have no experience of world-making; that the design argument, even if it works, only yields a limited designer, not the God of classical theism; and that the existence of evil and disorder in the world counts against the hypothesis of a benevolent designer. Hume's critique did not end natural theology, but it set the agenda for the debate.

Kant's critique was deeper. In the Critique of Pure Reason, Kant argued that the theistic arguments, including the ontological, the cosmological, and the teleological, all fail, because speculative reason cannot reach beyond experience to determine the existence of God. The ontological argument fails because existence is not a predicate, a property that adds to the concept of a thing. The cosmological argument depends on the ontological, because it moves from a necessary being to God, and the teleological argument yields only an architect, not a creator. Kant's critique closed natural theology as a project of theoretical reason, though Kant relocated the question to practical reason, where moral faith can be rational without theoretical proof.

The combined effect of Hume and Kant was to make natural theology look intellectually disreputable in the nineteenth and early twentieth centuries. The project was kept alive by the Roman Catholic tradition, especially in the work of the neo-Thomists, and by the more conservative Protestant tradition, but the analytic mainstream treated the theistic arguments as curiosities, not live options.

The Main Arguments

The contemporary revival of natural theology has produced a careful articulation of the main arguments. The cosmological argument, in its modern form, asks why there is something rather than nothing, and argues that the existence of the contingent world requires a necessary being as its ground. The argument has been developed by philosophers such as William Lane Craig, in the Kalam version, and by Richard Taylor and Robert Koons, in the contingent-cause version. The argument is contested, both in its premises and in its move from a necessary being to the God of classical theism.

The teleological argument, or argument from design, asks why the world appears fine-tuned for life, and argues that the fine-tuning is best explained by a designer. The contemporary version, developed by Richard Swinburne and by Robin Collins, draws on the physics of the early universe, where the constants of nature appear to be set within very narrow ranges that permit the existence of stable matter, chemistry, and life. The argument is contested by the multiverse hypothesis, which holds that there are many universes with different constants, and that the apparent fine-tuning is a selection effect.

The moral argument asks why there is objective moral value, and argues that moral value is best explained by a good God. The argument has been developed by C. S. Lewis, by Robert Adams, and by contemporary philosophers who hold that moral realism is more plausible on theism than on naturalism. The argument is contested by secular moral realists, who hold that moral truths are necessary truths and need no author, and by non-cognitivists, who deny that there are moral truths to explain.

The ontological argument, in its modern form, asks whether the very concept of God entails God's existence. The argument has been developed by Alvin Plantinga in a modal version, which argues that if a maximally great being exists in some possible world, it exists in all possible worlds, including the actual world. The argument is contested by those who deny that a maximally great being is possible, and by those who hold that existence is not a predicate, in line with Kant's critique.

The argument from religious experience, developed by Swinburne and by William Alston, argues that the widespread occurrence of religious experience provides prima facie evidence for the existence of the objects of those experiences. The argument is contested by those who hold that religious experience is better explained by psychology and culture, and by those who hold that the principle of credulity, that things are as they seem unless there is reason to think otherwise, does not apply in the religious case.

The Revival: Swinburne and Analytic Philosophy

The contemporary revival of natural theology was led by Richard Swinburne, in a series of books from The Coherence of Theism (1977) through The Existence of God (1979) and The Resurrection of God Incarnate (2003). Swinburne applies Bayesian probability theory to the theistic arguments and argues that the cumulative case, while no single argument is conclusive, raises the probability of theism above 0.5. The cumulative case is the heart of the contemporary project: no single argument is decisive, but the convergence of the cosmological, teleological, moral, and experiential arguments, together with the absence of a strong case against theism, makes theism more probable than not.

The revival has been matched by a revival of the critique. J. L. Schellenberg's argument from divine hiddenness, the contemporary problem of evil developed by J. L. Mackie and Paul Draper, and the explanatory challenge of naturalism, all press against the contemporary natural theology. The debate is live, and the state of the question is that the theistic arguments provide some support for theism, but whether that support is sufficient is disputed.

Natural Theology and Reformed Epistemology

A distinctive contemporary challenge to natural theology comes from Reformed epistemology. Alvin Plantinga has argued that natural theology is unnecessary for the rationality of theistic belief, because theistic belief can be properly basic, grounded in the sensus divinitatis. Plantinga does not reject natural theology, but he treats it as a confirmation of the properly basic belief, not as a foundation for it. The Reformed epistemologist's relation to natural theology is ambivalent: the arguments can be useful, but they are not necessary, and the demand for them, the evidentialist demand, is not well-founded.

The disagreement between natural theology and Reformed epistemology is a disagreement within theism, not between theism and atheism. Both hold that theistic belief is rational, but they disagree about why. The natural theologian holds that theistic belief is rational because the arguments support it. The Reformed epistemologist holds that theistic belief is rational because it is properly basic, and that the arguments are a useful but dispensable confirmation. The two views can coexist, and many contemporary theists hold both.

Contemporary Relevance

Natural theology remains a live project. The fine-tuning argument, in particular, has been strengthened by the physics of the early universe, and the moral argument has been strengthened by the revival of moral realism in analytic philosophy. The cosmological argument has been given new life by the Kalam version and by the work of contemporary metaphysicians on contingency and necessity. The project is not the dominant framework of analytic philosophy of religion, as it was in the medieval period, but it is a serious and respected research program.

The deeper lesson is that the question of God's existence is not settled by a single argument, but by the cumulative weight of the evidence, and by the philosophical assessment of what rationality requires. Natural theology is one answer to the question of how to assess the evidence, and its fate depends on the deeper questions of metaphysics, epistemology, and the philosophy of mind that the theistic arguments touch. The project is unfinished, but it is alive, and the work continues.

Sources

• Stanford Encyclopedia of Philosophy, "Philosophy of Religion" — https://plato.stanford.edu/entries/philosophy-religion/
• Stanford Encyclopedia of Philosophy, "Thomas Aquinas" — https://plato.stanford.edu/entries/aquinas/
• Stanford Encyclopedia of Philosophy, "David Hume" — https://plato.stanford.edu/entries/hume/
• Stanford Encyclopedia of Philosophy, "Kant's Philosophy of Religion" — https://plato.stanford.edu/entries/kant-religion/

Related Topics

• What Is Reformed Epistemology? — the alternative view.
• Is Faith Rational? — the question both views address.
• What Is Religious Experience? — one of the arguments.
• Who Bears the Burden of Proof for God? — the procedural question.
• Does God Exist? — the central question.
• Philosophy of God — the wider domain.