Philosophy of Religion: Theodicy, Fideism, and Religious Experience

Philosophy of religion is one of the most expansive and contested fields in philosophy. Its subject matter is not religion as a social or cultural phenomenon — that falls to sociology and anthropology — but the truth claims that religious traditions make: that God exists, that the world was created, that there is life after death, that certain texts are revealed. The philosophical question is not “why do people believe?” but “are there reasons to believe?” and “what does belief mean?”

This article surveys the major lines of the field, from arguments for God’s existence to religious experience, theodicy, fideism, and pluralism.

1. Philosophy of Religion and Theology: A Necessary Distinction

Theology typically operates from within a religious tradition. It works with scriptures, dogmas, and the teaching authority of a faith community. Its aim is to understand and systematize a faith already held — fides quaerens intellectum, as Anselm (c. 1033–1109) put it.

Philosophy of religion, by contrast, adopts a stance of critical, independent inquiry. It presupposes no particular religious tradition as true; it interrogates religious claims on the basis of reasons that are public and assessable by anyone. In principle, an atheist can practice philosophy of religion with the same rigor as a believer.

This distinction is operational rather than rigid: some of the greatest philosophers of religion — Thomas Aquinas (1225–1274), Alvin Plantinga (b. 1932), Richard Swinburne (b. 1934) — are also theologians. What makes them philosophers is that they argue from reasons, not from authority.

Natural theology occupies the boundary zone: it is the project of establishing truths about God — his existence, his attributes — using reason alone, without appeal to revelation. The classical proofs of God’s existence belong to natural theology.

2. Arguments for the Existence of God

2.1 The Ontological Argument

Anselm of Canterbury formulated the ontological argument in the Proslogion (1077–1078): God is “that than which nothing greater can be conceived” (id quo nihil maius cogitari possit). Such a being must exist not only in the understanding but in reality — for what exists in reality is greater than what exists in thought alone. Therefore God exists.

The modal version was reformulated by Alvin Plantinga in The Nature of Necessity (1974) and God, Freedom, and Evil (1974): if it is possible for a maximally excellent being to exist (one possessing omnipotence, omniscience, and perfect goodness in every possible world), then such a being exists in the actual world. The key premise is the claim of possibility; Plantinga acknowledges that one who denies the conclusion may deny this premise, but argues that the argument is valid and its premises rationally defensible.

The classic objection comes from Immanuel Kant (1724–1804): “being is not a real predicate” (Sein ist kein reales Prädikat, Critique of Pure Reason, B626). Existence adds no determination to a concept; it merely affirms that an object corresponds to the concept. The ontological argument, Kant charges, conflates conceptual analysis with actual existence.

2.2 The Cosmological Argument

Thomas Aquinas presented in the Summa Theologiae (I, q.2, a.3) the Five Ways, all a posteriori: motion, efficient causality, contingency, degrees of perfection, and the governance of things all converge on a first, necessary, and intelligent Being.

Leibniz (1646–1716) refined the cosmological argument through the principle of sufficient reason: nothing happens without a sufficient reason for why it is thus and not otherwise. The sufficient reason for the contingent world cannot lie within the world — it must lie in a Being whose reason for existence is in itself. The question “pourquoi il y a plutôt quelque chose que rien?” — why is there something rather than nothing? (Principles of Nature and Grace, 1714, §7) — became the canonical formulation of the fundamental metaphysical question.

2.3 The Teleological Argument and Hume’s Critique

The teleological argument (the design argument) infers the existence of an intelligent designer from the order and complexity of the world. Popularized by William Paley (1743–1805) in the watchmaker metaphor, it has ancient roots: it is Thomas’s fifth Way and runs through the entire tradition.

David Hume (1711–1776), in the Dialogues Concerning Natural Religion (written in the 1750s and published posthumously in 1779), subjected it to a systematic critique through the character Philo: (1) the analogy between the world and a machine is weak — we do not observe universes being manufactured; (2) order could result from other principles (generation, chance operating over sufficient time); (3) even granting a designer, nothing ensures that it is unique, perfect, or morally good.

In the contemporary context, the Intelligent Design movement (Michael Behe, Darwin’s Black Box, 1996; William Dembski) attempted to reformulate the teleological argument in biological terms — the “irreducible complexity” of certain cellular structures. Scientific critics (Elliott Sober, Kenneth Miller, and others) have challenged these claims empirically; philosophically, debate about the argument’s inferential validity continues.

3. The Problem of Evil and Theodicy

The problem of evil is perhaps the most powerful objection to theism. In its logical version: if God is omnipotent, omniscient, and perfectly good, evil cannot exist; but evil does exist; therefore God does not exist. In the evidential version (more modest): the quantity and character of evil in the world makes the theistic hypothesis unlikely to be true.

3.1 Leibniz’s Theodicée

The very term “theodicy” was coined by Leibniz as the title of his Essais de Théodicée sur la bonté de Dieu, la liberté de l’homme et l’origine du mal (1710) — the only major philosophical work he published in his lifetime. The problem: how to reconcile a good and all-powerful God with the existence of evil?

Leibniz’s response begins with the notion of possible worlds: in creating, God chose among infinitely many possible worlds. A world with no evil whatsoever is not logically possible — for creation entails limitation, and every finite thing is imperfect. The actual world is therefore “the best of all possible worlds” (le meilleur des mondes possibles) — not the best of all conceivable worlds, but the best among those that are logically realizable. Voltaire ridiculed this position in Candide (1759) following the Lisbon earthquake (1755), which killed tens of thousands.

3.2 The Free Will Defense: Plantinga

Alvin Plantinga, in God, Freedom, and Evil (1974), formulated the Free Will Defense: it is logically possible that God could not create free creatures who always choose the good — for that would be contradictory (beings who necessarily choose the good do not exercise free will in the relevant sense). Therefore the existence of moral evil does not logically contradict the existence of an omnipotent and good God.

Plantinga distinguishes a defense (which need only show that there is no logical contradiction) from a theodicy (which claims to explain why God permits evil). The defense does not answer why there is evil, but establishes that it is not contradictory to suppose God and evil coexisting.

The response has acknowledged limits: it addresses moral evil (produced by free agents) but not natural evil (disease, natural disasters). Plantinga proposed an extension to natural evil involving free spiritual agents, but this move has been widely regarded as speculative.

3.3 The Evidential Problem: William Rowe

William Rowe (1931–2015) formulated the evidential problem of evil: even without logical contradiction, the extent and intensity of suffering — especially the suffering of innocents and of animals, which serves no “educational” purpose — makes the theistic hypothesis improbable. Rowe’s paradigm case: a fawn that dies slowly in a forest fire, unknown to anyone, yielding no conceivable benefit. If God exists, why permit this suffering?

Theistic responses include: (a) sceptical theism (Stephen Wykstra, Michael Bergmann) — given human cognitive limitations, we cannot judge that God lacks sufficient reason to permit suffering; (b) John Hick’s soul-making theodicy (drawing on Irenaeus of Lyons) — suffering is a condition for the spiritual and moral development of human beings.

4. Fideism: Faith Beyond Reason

Fideism is the position that religious faith does not require — or is not susceptible to — rational justification. There are moderate variants (reason is insufficient but not contrary to faith) and radical ones (faith is by definition contrary to reason).

4.1 Kierkegaard: the Leap into the Absurd

Søren Kierkegaard (1813–1855), in Fear and Trembling (Frygt og Bæven, 1843) and Philosophical Fragments (Philosophiske Smuler, 1844), argues that the relationship with God is not mediated by rational systems — Hegel and philosophical speculation are the explicit targets. Faith is an absolutely personal relation with the Absolute, demanding what Kierkegaard calls the leap (Spring): a decision that goes beyond the guarantees of reason.

The paradigm case is Abraham in Fear and Trembling: God commands Abraham to sacrifice his son Isaac. Rationally, the act is murder and the destruction of what is most precious. Yet Abraham, the “knight of faith,” acts against every universal ethical mediation in direct obedience to the Absolute. Kierkegaard does not prescribe this path for everyone — but uses it to show that authentic faith inhabits a register that ethics and reason cannot reach.

4.2 Wittgenstein and D. Z. Phillips

Ludwig Wittgenstein (1889–1951), in his Lectures on Religious Belief (student notes, published posthumously 1966) and On Certainty (Über Gewissheit, posthumous 1969), suggested that religious beliefs function differently from empirical hypotheses. They are not theories about the world that could be confirmed or refuted; they are regulative pictures that structure an entire form of life.

D. Z. Phillips (1934–2006), following this lead, developed what came to be called Wittgensteinian fideism: religious language has its own grammar, and applying external empirical criteria of verification to it is a categorical mistake. In The Concept of Prayer (1965) and Religion Without Explanation (1976), Phillips argues that asking whether God “really exists” presupposes an mistaken model of what religious belief is.

Critics such as Kai Nielsen argue that this position immunizes religion against all rational criticism, which would equally immunize delusion or superstition.

5. Natural and Revealed Religion

The distinction between natural religion (known by reason alone) and revealed religion (known by divine revelation) structures much of modern philosophy of religion.

Hume, in the Dialogues, examined the limits of natural religion: even granting that one can reach some conclusion about a creator of the world, none of the specific doctrines of the historical religions — incarnation, resurrection, particular providence — follows from it. The passage from natural theology to revealed theology requires a leap that reason does not justify.

Kant, in Religion within the Bounds of Mere Reason (Die Religion innerhalb der Grenzen der bloßen Vernunft, 1793), proposed that genuinely rational religion is entirely moral: God is postulated by practical reason, and external worship, historical dogmas, and rites are “religious illusion” (Afterdienst) insofar as they substitute for authentic morality. Revealed religion has value only insofar as it expresses the moral law.

6. Religious Experience

Religious experience — the perception of God, the oceanic feeling, conversion, mysticism — plays a central role in contemporary philosophy of religion, especially as indirect evidence for theism.

6.1 William James

William James (1842–1910), in The Varieties of Religious Experience (1902), offered an empirical and pragmatic analysis of religious experience. James identified recurring characteristics of mystical experiences: ineffability (they cannot be adequately expressed in words), noetic quality (they convey knowledge), transciency, and passivity. His philosophical assessment is pragmatic: if religious experience produces positive fruits in life (serenity, generosity, meaning), this constitutes evidence that something real is at stake — not necessarily the personal God of theism, but a “more” that transcends individual consciousness.

6.2 Alston and the Perception of God

William Alston (1921–2009), in Perceiving God: The Epistemology of Religious Experience (1991), developed the most rigorous argument for religious experience as epistemic evidence. His central thesis: the epistemic practices through which people perceive God (Mystical Perceptual Doxastic Practice) are structurally analogous to the epistemic practices through which we perceive the physical world. There is no consistent reason to accept sensory perception as a source of knowledge while rejecting religious experience as a source of justified belief about God.

Alston acknowledges that religious perceptual practices are not circular in the same way as sensory perception, and that there are important differences. But he maintains that, in the absence of positive refutation, it is epistemically rational to accept beliefs formed in these practices.

6.3 Swinburne and the Principle of Credulity

Richard Swinburne, in The Existence of God (1979; 2nd ed. 2004), formulated the principle of credulity: in general, we should believe things are as they appear to be, unless there are special reasons for doubt. If someone appears to perceive the presence of God, this is prima facie evidence that God is present. Combined with the principle of testimony (we should believe that others have had the experiences they report), the cumulative evidence of religious experiences contributes to the overall probability of theism.

7. Philosophical Atheism: J. L. Mackie

Philosophical atheism received one of its most rigorous expressions in J. L. Mackie (1917–1981). In “Evil and Omnipotence” (1955, Mind) he presented the logical problem of evil with analytic clarity. In The Miracle of Theism (1982), published posthumously, Mackie systematically examined each theistic argument and concluded that none provides sufficient reason to believe in God. The book is regarded as one of the most rigorous documents of twentieth-century philosophical atheism.

Mackie argued specifically against Plantinga’s Free Will Defense: an omnipotent God could have created beings with freedom who nonetheless always chose the good — for omnipotence has no logical limits. Plantinga replies that this is contradictory: a being who necessarily chooses the good does not exercise free will in the relevant sense.

8. Religious Pluralism: John Hick

One of the most unsettling questions for philosophy of religion is the diversity of religions. If the Christian God exists, what to make of Allah, Brahman, Buddhist Nirvana? Are they all the same? Are all but one false?

John Hick (1922–2012), in God and the Universe of Faiths (1973) and An Interpretation of Religion (1989), proposed religious pluralism: the great religious traditions are culturally conditioned human responses to one and the same ultimate Reality (the Real), which transcends any conceptualization. All traditions offer equally valid paths to salvation and liberation. Hick draws on Kant’s distinction between thing-in-itself and phenomenon: the Real an sich is unknowable; what we know are the cultural “icons” that each tradition constructs.

Critics including Alvin Plantinga, Keith Ward, and Gavin D’Costa argue that Hick’s pluralism is self-contradictory: in claiming that the Real transcends all categories, Hick still makes positive claims about it; and in equating all traditions, he ignores the doctrinal differences that the traditions themselves regard as essential.

9. Contemporary Perspectives

Analytic philosophy of religion has flourished in recent decades with contributions from Eleonore Stump (Aquinas, 2003; Wandering in Darkness, 2010), who combines analytic rigor with Thomistic exegesis; Paul Moser (The Elusive God, 2008), who redefines what counts as adequate evidence for God; and Peter van Inwagen (The Problem of Evil, 2006), who develops responses to the evidential problem. On the continental side, Jean-Luc Marion (Dieu sans l’être, 1982) proposes thinking God beyond being, as givenness (donation).

10. Conclusion

Philosophy of religion does not adjudicate between theism and atheism — that is not its task. Its task is clarification: Are the arguments valid? Does experience constitute evidence? Is faith rational or irrational? Is evil logically or evidentially incompatible with a good God?

What the field has established is that none of the positions — theist, atheist, or agnostic — is obviously correct. The problem of God’s existence remains one of philosophy’s most resistant because it stands at the intersection of epistemology, metaphysics, ethics, and philosophy of language. This is not a deficiency of the field — it is a sign that the question is genuinely deep.

Essential Reading

• Hume, Dialogues Concerning Natural Religion (posthumous, 1779).
• Kant, Religion within the Bounds of Mere Reason (1793).
• Kierkegaard, Fear and Trembling (1843); Philosophical Fragments (1844).
• William James, The Varieties of Religious Experience (1902).
• Leibniz, Theodicy (1710).
• Alvin Plantinga, God, Freedom, and Evil (1974); The Nature of Necessity (1974).
• Richard Swinburne, The Existence of God (1979; 2nd ed. 2004).
• J. L. Mackie, The Miracle of Theism (1982).
• William Alston, Perceiving God (1991).
• John Hick, An Interpretation of Religion (1989).
• D. Z. Phillips, Religion Without Explanation (1976).

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