You are viewing a free preview of this lesson.
Subscribe to unlock all 10 lessons in this course and every other course on LearningBro.
The relationship between faith and reason is one of the oldest and most fundamental questions in the philosophy of religion. Can belief in God be rationally justified, or does genuine faith require a leap beyond — or even against — reason? Behind the question lie two rival pictures of what religious belief is. On one picture, faith is the crown of a rational enterprise: reason lays the foundations, and faith builds upon them. On the other, faith is a passionate inward commitment that the cool procedures of argument can neither establish nor undermine — and that may even be cheapened by the demand for proof. This lesson sets out the major positions: Aquinas's confidence that faith and reason are complementary; the fideism of Tertullian and Kierkegaard, for whom faith outruns or defies reason; Pascal's pragmatic wager; Plantinga's reformed epistemology, which argues that belief in God can be rational without being based on argument at all; and Barth's insistence that natural reason cannot reach God. The aim is not merely to describe these views but to weigh them — to ask which best captures what it means to believe.
St Thomas Aquinas (1225–1274) represents the classical position that faith and reason are complementary, not contradictory. In the Summa Theologica and Summa Contra Gentiles, Aquinas argued that human reason, operating independently of revelation, can establish certain truths about God — including God's existence, God's unity, and some of God's attributes such as power, wisdom and goodness. This enterprise is known as natural theology: theology done "from below," reasoning from the created order up towards its creator.
Key term: Natural theology — the attempt to establish truths about God through unaided human reason and observation of the natural world, without reliance on special revelation (Scripture, prophecy, religious experience).
Aquinas's Five Ways — the arguments from motion, efficient causation, contingency, gradation (degrees of perfection), and the governance of things (teleology) — are the most famous examples of natural theology. Each begins with an observable feature of the world and reasons to God as its ultimate explanation. For Aquinas these are genuine demonstrations a posteriori: starting from effects available to anyone, they reason back to a cause. Crucially, Aquinas did not think we can demonstrate God's existence a priori — he rejected Anselm's ontological argument precisely because God's essence is not evident to us. Knowledge of God begins with the senses and the world, not with the mere concept of God.
Aquinas distinguished between two categories of religious truth:
| Category | What it covers | Examples | How it is known |
|---|---|---|---|
| Preambles of faith (praeambula fidei) | Truths about God accessible to reason | God's existence, unity, incorporeality | Demonstration / natural reason |
| Articles of faith (articuli fidei) | Truths exceeding reason, disclosed by God | The Trinity, the Incarnation, the Resurrection | Special revelation, accepted by faith |
The preambles are, in principle, accessible to reason; the articles require divine revelation and are received by faith. Aquinas's careful claim is that the preambles are believed by most people on the authority of revelation rather than worked out by argument — most believers do not in fact prove God's existence — but they could be demonstrated, which is what matters for the relation of faith to reason. Crucially, the two can never genuinely contradict, since reason and revelation have a single source in God, the author of all truth. If a philosophical conclusion appears to contradict revealed truth, there must be an error in the reasoning rather than a real conflict between faith and reason.
Aquinas's guiding axiom — gratia non tollit naturam sed perficit ("grace does not destroy nature but perfects it") — expresses his conviction that the supernatural builds upon and elevates the natural rather than overriding it. Reason provides the foundation; faith completes the structure. The philosopher can know that God exists; the believer, through revelation, can know who God is — that God is triune, incarnate and redeeming. Faith, for Aquinas, is not irrational; it is supra-rational, taking the mind further than it could travel under its own power, but in the same direction.
It is worth dwelling on what Aquinas means by calling faith supra-rational rather than contra-rational. The articles of faith — that God is three persons in one substance, that the eternal Son became incarnate — are not, for Aquinas, contradictions that reason can see to be false. They are mysteries that exceed the natural reach of the human intellect, which in this life knows by abstracting from sense-experience and therefore struggles with realities that have no sensory analogue. A finite mind cannot fully comprehend the infinite, just as a person born blind cannot fully grasp colour; but the limitation lies in us, not in any incoherence in the object. This is the crucial difference from Kierkegaard, who will say that the Incarnation is not merely above reason but an offence to it, a paradox. For Aquinas the articles are credible — reason can show that they are not impossible, can defend them against objections, and can draw out their implications — even though it cannot prove them. Faith therefore involves the will as well as the intellect: the intellect assents to the articles not because it sees their truth directly but because it is moved by the will, under grace, to trust the God who reveals them. Faith is, in his famous definition, a "mean between knowledge and opinion" — more certain than opinion (because it rests on God's authority) yet lacking the vision that knowledge enjoys.
This careful architecture is also what makes Aquinas vulnerable. If the whole edifice rests on the preambles — above all the demonstrability of God's existence — then the well-known objections to the Five Ways (Hume on causation and the fallacy of composition; Russell's "the universe is just there"; Kant on the limits of the cosmological argument) threaten the foundation. Should the demonstrations fail, Aquinas's elegant ordering of reason-then-faith would lose its base, and his confidence that faith and reason are partners would look like an unredeemed promissory note. A defender can reply that Aquinas needs only that God's existence be demonstrable in principle, and that even the contested Five Ways shift the burden of proof; but the dependence remains a real exposure.
Fideism is the family of views holding that faith is independent of — and may even be contrary to — reason. The fideist denies that religious belief stands in need of rational justification, and denies that it can be established or overturned by philosophical argument. Faith is its own authority.
Key term: Fideism — the view that religious belief rests on faith rather than reason, and neither requires nor admits of rational proof; in its strong form, faith may even run against reason.
| Thinker | Position |
|---|---|
| Tertullian (c. 155–240) | Asked "What has Athens to do with Jerusalem?" — implying that pagan philosophy has nothing to contribute to Christian faith. The slogan credo quia absurdum ("I believe because it is absurd") is traditionally associated with him; what he actually wrote (of the death of the Son of God) was credibile est, quia ineptum est — "it is to be believed because it is unfitting." |
| Blaise Pascal (1623–1662) | "The heart has its reasons of which reason knows nothing" (Pensées). For Pascal, God is "hidden" (Deus absconditus), and it is the heart, not abstract metaphysics, that perceives God. |
| Martin Luther (1483–1546) | Polemically called reason "the Devil's whore" when reason sets itself up to judge the things of God — though Luther freely used reason in ordinary and academic matters. |
Soren Kierkegaard (1813–1855), the Danish philosopher often called the father of existentialism, mounted the most powerful modern fideist challenge to Aquinas's confidence in natural theology. The attempt to prove God, he argued, misunderstands what faith is. Faith is not the conclusion of a syllogism; it is a passionate, personal appropriation made in the teeth of uncertainty. Writing under the pseudonym Johannes Climacus in the Concluding Unscientific Postscript (1846), Kierkegaard declared: "If I am capable of grasping God objectively, I do not have faith; but because I cannot do this, I must have faith." The objective uncertainty of God's existence is not an obstacle to faith but its very precondition. Were God's existence demonstrable with mathematical certainty, faith — and the risk that gives faith its worth — would dissolve.
Key term: Leap of faith — Kierkegaard's image (more precisely a leap, a qualitative transition) of the movement by which the individual embraces God in passionate inwardness, beyond what objective reason can secure.
Kierkegaard distinguished sharply between objective and subjective truth. Objective truth concerns what is said — whether a proposition corresponds to reality. Subjective truth concerns how it is held — the manner in which an existing person relates to it. Religious truth, for Kierkegaard, is essentially the second: "An objective uncertainty, held fast in an appropriation-process of the most passionate inwardness, is the truth, the highest truth attainable for an existing individual." The person who clings to God amid uncertainty stands in a deeper relation to truth than one who files God away as a settled intellectual conclusion. And the supreme object of faith — that the eternal God entered time as a particular human being in Jesus Christ — is the "absolute paradox," not merely hard to grasp but an offence to reason, which is exactly why it summons faith rather than assent.
Kierkegaard mapped three "stages" or spheres through which a self may pass:
| Sphere | Governing concern | Why it breaks down |
|---|---|---|
| Aesthetic | Pleasure, novelty, immediacy; living "in the moment" | Collapses into boredom and despair; the self has no continuity or commitment |
| Ethical | Duty, responsibility, universal moral law | Confronts the individual with guilt it cannot discharge; the ethical cannot save |
| Religious | A passionate, personal relation to God in faith | Reached not by argument but by a leap; lived as a paradox before God |
The movement between spheres is not achieved by tidy reasoning but by a qualitative decision that re-orders the whole self. Importantly, Kierkegaard's fideism is not a celebration of irrationality for its own sake: it is the claim that the deepest human truth is the kind one must live, stake a life on, and suffer — not the kind one establishes from a neutral standpoint.
It helps to see what Kierkegaard is attacking. His target is the cultured Christendom of nineteenth-century Denmark, in which (as he saw it) everyone was nominally a Christian by accident of birth, faith had been reduced to comfortable doctrinal agreement, and the existential demand of the gospel had been domesticated into respectability. Against this he wields the category of the individual: one does not become a Christian en masse or by inheriting a creed, but only by a personal, fear-and-trembling appropriation that cannot be delegated to the crowd, the professor, or the established church. This is why "subjectivity is truth" is not the relativist slogan it is sometimes mistaken for. Kierkegaard is not saying that any belief is true if held sincerely; he is making a claim about the kind of truth that religious truth is — a truth that must be existed, inhabited with one's whole life, rather than catalogued. A person could have the entire content of Christianity objectively correct and still, in Kierkegaard's sense, lack the truth, if they relate to it as a spectator. Conversely, the passionate believer reaches "the highest truth attainable for an existing individual" precisely through the uncertainty, not in spite of it. The risk is not a regrettable feature to be minimised but the very medium in which faith becomes real.
Blaise Pascal's Wager offers a different route again — neither natural-theological proof nor pure leap, but a pragmatic argument from self-interest under uncertainty. Reason, Pascal grants, cannot settle whether God exists: "Reason can decide nothing here." But we must nonetheless "wager," because suspending the question is itself a way of living without God. He then weighs the outcomes: stake your life on God and, if God exists, you gain "an infinity of an infinitely happy life"; if God does not exist, you have lost very little. Wager against God and you risk infinite loss for a trivial finite gain. Since a finite stake against an infinite prize is rationally compelling, the prudent course is to "bet that He exists."
Key term: Pascal's Wager — a pragmatic argument that, given the possible infinite gain and merely finite loss, it is rational to live as if God exists even where reason cannot prove that He does.
Pascal anticipated the obvious objection — I cannot simply will myself to believe — by advising the unbeliever to act the part: to follow religious practices, "taking holy water, having masses said," until belief follows habit. Critics press several lines: belief produced by self-interest is not the trusting love a perfect God would want (the wrong-kind-of-reason objection); the wager assumes a single God who rewards belief, ignoring rival faiths and the possibility of a God who prizes honest doubt (the many-gods objection); and one cannot believe to order, so the advice to "deaden" one's reason looks like a recommendation to self-deceive. Defenders reply that Pascal addresses someone already drawn to faith but held back by intellectual scruple, for whom the wager removes a bad reason to refuse the leap.
The wager also illuminates a structural point about the whole topic. Pascal grants the fideist premise — that reason cannot settle the question of God — yet refuses the bare-fideist conclusion that nothing rational can be said. Instead he reframes the question from theoretical rationality ("is it true?") to practical rationality ("how should I live, given that I cannot know?"). This is a genuinely distinct contribution, and it foreshadows William James's "The Will to Believe" (1896), which argues that where a choice between hypotheses is "living, forced and momentous," and cannot be decided on evidence, we have the right to let our "passional nature" decide rather than suspend judgement forever. James's worry, against Clifford's evidentialism, is that the rule "never believe without sufficient evidence" can itself cost us truths — it is a way of risking error avoidance at the price of truth loss. Pascal and James together mark out a third territory between Aquinas's proofs and Kierkegaard's leap: the pragmatic defence of religious belief, which neither demonstrates God nor abandons reason but redeploys reason in the register of action and life-commitment. The standard reservation is that practical rationality cannot, by itself, make a belief true — it can at most make believing prudent — so the pragmatic route answers "should I believe?" without answering "is it so?".
Alvin Plantinga (1932–2025) developed reformed epistemology — the claim that belief in God can be perfectly rational without being based on evidence or argument. His target is classical foundationalism: the view that a belief is rational only if it is either self-evident, evident to the senses, or incorrigible — or else supported by evidence tracing back to such beliefs. The atheologian's demand "Where is your evidence for God?" presupposes this picture (it is the unspoken premise of W. K. Clifford's "evidentialism": "it is wrong always, everywhere, and for anyone, to believe anything upon insufficient evidence").
Plantinga's first move is to turn the criterion on itself. The classical foundationalist's own thesis — a belief is rational only if it is self-evident, evident to the senses, incorrigible, or based on such beliefs — is not itself self-evident, evident to the senses or incorrigible, nor can it be derived from beliefs that are. By its own standard it is irrational. Classical foundationalism is therefore self-refuting, and with it falls the assumption that theistic belief must be propped up by argument to be respectable.
Key term: Reformed epistemology — Plantinga's view that belief in God can be "properly basic": a foundational belief that is rational even though it is not inferred from, or supported by, other beliefs or evidence.
A basic belief is one not held on the basis of other beliefs. We hold many such beliefs entirely reasonably: that there is a tree before me (perception), that I had breakfast (memory), that other people have minds and feelings. None is proved; each is occasioned by experience and accepted without argument. Plantinga argues that belief in God belongs in this company. It too can be properly basic — basic and rational — when it arises in the right circumstances:
These experiences are the grounds of theistic belief, just as being appeared-to in a tree-ish way grounds belief in the tree. The belief is not groundless or arbitrary; it is simply not the product of inference. Plantinga is careful to add (against the "Great Pumpkin" objection that any belief could be declared basic) that proper basicality has conditions — the belief must be produced by properly functioning faculties, in an appropriate environment, aimed at truth.
Drawing on John Calvin (1509–1564), Plantinga posits a sensus divinitatis — an innate cognitive faculty or disposition that, when triggered by the appropriate circumstances, produces belief in God. It is to the divine what perception is to the physical world. In his mature account (Warranted Christian Belief, 2000) he frames this in terms of warrant: a belief has warrant when it is produced by faculties functioning properly, in a suitable environment, according to a design plan successfully aimed at truth. If there is a God who has so designed us, then theistic belief produced by the sensus divinitatis has warrant and constitutes knowledge. Sin, on Calvin's account, has damaged but not destroyed this faculty, which is why belief is not universal.
There is a sting in the tail. Plantinga concedes that whether theistic belief has warrant depends on whether it is true — on whether there really is such a God and faculty. So reformed epistemology does not prove God exists; it shows that the de jure objection (that theistic belief is irrational whether or not God exists) cannot be sustained independently of the de facto question (whether God exists). Critics — including those sympathetic to the project — object that the sensus divinitatis looks like an ad hoc postulate that conveniently insulates belief from criticism, and that the same structure would license the "properly basic" beliefs of contradictory religions, leaving us no way to adjudicate between them.
Standing at the opposite pole from Aquinas, Karl Barth (1886–1968) denied natural theology altogether. Human reason, corrupted by sin, cannot ascend to God; God is known only where God freely chooses to reveal himself, supremely in Jesus Christ. Any attempt to build a bridge from creation or conscience to God is, for Barth, not merely inadequate but idolatrous, because it makes a god in the image of human reasoning. His thunderous "Nein!" to Emil Brunner's modest "point of contact" expresses the conviction that grace must be wholly God's gift, owing nothing to a human capacity. For the faith–reason debate, Barth represents the strongest claim that the two are not partners at all: reason has no road to God, and faith is a response to revelation, not a conclusion of inquiry.
It is worth seeing precisely why Barth thought natural theology dangerous rather than merely mistaken. His worry was theological, not just epistemological. If human beings can reach God by their own reasoning, then the knowledge of God becomes a human achievement, and the initiative passes from God to us. The God so reached is, moreover, the God that our reasoning constructs — a First Cause, a Designer, a Necessary Being — and this "God of the philosophers" is, Barth feared, an idol that we then identify with the living God of Jesus Christ. Worse, Barth wrote against the background of the German church's accommodation to Nazism, in which appeals to "orders of creation" and natural revelation were used to baptise nationalist ideology. The Barmen Declaration (1934), which Barth largely drafted, insisted that the church listens to "one Word of God" alone — Jesus Christ — and rejects "other events and powers, forms and truths, as God's revelation." For Barth, then, the rejection of natural theology was a matter of the church's very integrity, not academic caution.
A thread running through the whole debate is the suspicion that faith without rational grounding collapses into wishful thinking. Sigmund Freud gave this suspicion its classic form: religious belief is the projection of an infantile wish for a protective father onto the cosmos — an "illusion" born of need rather than evidence. The fideist seems peculiarly exposed to this charge: if faith neither rests on argument nor answers to evidence, what distinguishes the leap of faith from self-deception, or from the believer in any number of incompatible religions, each making their own leap?
The positions surveyed here can be read as so many answers to this charge. Aquinas answers by anchoring faith to reason at the base: the preambles are demonstrable, so faith is not built on nothing, even though its higher articles outrun proof. Plantinga answers by redescribing rationality: the demand for evidence is itself unsupported, and theistic belief, produced by properly functioning faculties in response to experience, is no more wishful than perception or memory. Mitchell-style trust (developed in the religious-language debate but relevant here) answers by acknowledging counter-evidence: the believer who admits that suffering tells against "God is good," yet holds on because of a prior encounter, is not engaged in the breezy denial Freud describes. Kierkegaard, strikingly, embraces part of the charge and turns it: yes, faith is a risk taken without objective security — but that risk, consciously held in passionate inwardness, is precisely what distinguishes living faith from the dead assent that Freud's caricature actually targets. The least satisfying answer is bare fideism that simply refuses the question, since it cannot explain why one leap is wiser than another.
Key term: Evidentialism — the principle (classically W. K. Clifford) that it is wrong to believe anything on insufficient evidence; the assumption that Plantinga argues is self-refuting and that frames much of the suspicion of faith.
This is why the quality of an answer to "is faith rational?" depends so heavily on what "rational" is taken to mean. If rationality requires proof before belief, almost every position here except Aquinas's preambles fails, and faith looks irresponsible. If rationality requires only that belief be responsibly held, answerable to reasons, and not demonstrably absurd, then Aquinas, Plantinga and Mitchell-style trust all clear the bar, and even Kierkegaard's leap can be defended as a reasoned decision about the limits of reason rather than a flight from it. The examiner's prize goes to candidates who notice that the whole dispute often turns on this unstated definition.
A useful bridge between Aquinas and the fideists is Anselm of Canterbury (1033–1109), whose motto fides quaerens intellectum — "faith seeking understanding" — captures a third possibility. For Anselm, one does not reason one's way to faith; rather, one begins within faith and then seeks to understand what one already believes. "I do not seek to understand in order that I may believe, but I believe in order that I may understand" (Proslogion). This is neither Aquinas's confidence that reason can reach God from outside, nor Kierkegaard's claim that proof would destroy faith; it is the view that faith and reason are sequenced — faith first, understanding following. It shows that "faith and reason" need not be rivals competing for the same ground: they can be partners in which one prepares the way for the other. Candidates can use Anselm to complicate any essay that assumes faith and reason must be either identical (rationalism) or opposed (fideism).
| Position | Can reason reach God? | What is faith? | Key risk |
|---|---|---|---|
| Aquinas | Yes — preambles demonstrable; articles by revelation | Supra-rational assent completing reason | Over-claims what the Five Ways prove |
| Kierkegaard | No — proof would destroy faith | Passionate inward leap embracing paradox | Faith may become indistinguishable from wishful thinking |
| Pascal | No — but prudence can guide | A wager prompting the will toward belief | Self-interested or self-deceiving belief |
| Plantinga | Argument unnecessary | Properly basic belief, grounded in experience | Sensus divinitatis may be ad hoc; rival "basic" beliefs |
| Barth | No — reason is corrupted | Obedient response to revelation in Christ | Severs faith from rational accountability |
Mid-band approach. A weaker response would list the thinkers — Aquinas thinks faith and reason agree, Kierkegaard thinks faith is a leap, Plantinga thinks belief is properly basic — and then assert a preference without argument, or simply conclude "it depends on the person." Knowledge may be accurate, but it is inert: there is no sustained line of reasoning, and the evaluative claims are stated rather than earned.
Stronger approach. A stronger response frames a genuine thesis. It might argue that the statement assumes precisely what is in dispute — namely an evidentialist picture of rationality — and that Plantinga's self-refutation argument dismantles that picture: if "rational belief requires evidence" cannot itself be supported by evidence, the demand collapses. It would then show that Aquinas need not be read as the opponent of this claim he first appears: Aquinas holds that the preambles are demonstrable but the articles (Trinity, Incarnation) are not, so even the great rationalist of the tradition concedes that the core of faith outruns proof. This already complicates the essay title, and the candidate would signpost that it does.
Top-band judgement. The most convincing answer reaches a substantiated verdict rather than a verdict-shaped shrug. It might conclude that the statement is true on a weak reading and false on a strong one. If "supported by reason" means "not demonstrably irrational, and answerable to reasons," then yes — faith should be rationally accountable, which is why Aquinas's harmony and Plantinga's conditions on proper basicality are attractive, and why pure fideism's inability to discriminate between rival faith-claims is a serious cost. But if "supported by reason" means "established by argument before belief is permitted," then the demand is both self-undermining (Plantinga) and false to the phenomenon (Kierkegaard): the believer who must first prove God does not yet have the trusting relationship that faith names. The judgement is therefore that faith must be reasonable without being proven — a conclusion defended, not merely announced, by playing the strongest version of each position against the title.
Examiner-style commentary. What lifts this response is that it interrogates the question rather than answering a question of its own choosing: it notices the loaded word "supported" and distinguishes two readings, which is the move that turns description into evaluation. It deploys scholars as instruments of argument (Plantinga's self-refutation does real work; Aquinas's preambles/articles distinction is used to destabilise the title) rather than parading them. The counter-positions are given their strongest form before being weighed, and the conclusion follows from the body rather than appearing from nowhere. Precise terminology — praeambula fidei, properly basic, evidentialism — is used accurately and economically. That combination of a controlled thesis, balanced critical engagement, and a judgement that is genuinely reached is the mark of the top band.
Exam tip: Examiners reward candidates who use the loaded wording of the question. When a title equates rationality with "evidence" or "proof," show that this is a contestable picture (Plantinga's self-refutation argument) and distinguish "reasonable" from "proven." Always cite Aquinas's preambles/articles distinction precisely — it is the single most useful discriminator in this topic.