The Faith and Reason Controversy — Why It Arose, What It Demanded, and Why Neither Extreme Could Satisfy

Introduction — A Problem That Did Not Exist in Greek Philosophy

To understand why the faith-reason controversy is distinctively medieval — why it did not exist in Greek philosophy and why it is unavoidable in the Christian philosophical tradition — we need to begin with the most basic difference between the two traditions: the difference in what each was trying to understand.

For Greek philosophy, the object of knowledge was the natural world and human experience within it: what is the human being? how should we live together in political communities? what is the structure of the natural world and what are its laws? These are questions that fall squarely within the domain of reason and experience. The Greek philosopher needed no revelation to investigate them. Plato observed human relationships and argued about justice from what he could see. Aristotle dissected animals and recorded his observations. Neither needed a supernatural source for the knowledge they were seeking, because the things they were seeking to know were accessible through the faculties they already possessed.

Medieval philosophy changed the object of investigation. The primary concern was no longer the human being or the natural world — it was God and the supernatural. And here the situation changes completely. God, in the Christian understanding, is not part of the natural world. God is infinite; the world is finite. God is eternal; the world is temporal. The gap between God and the created world is not a difference of degree — it is a difference of kind. No amount of studying the world, however careful and systematic, will tell you anything about God, because God is not the kind of thing that shows up in the world.

The crucial consequence:  If God is completely separate from the world, and if reason and experience can only reach what is in the world, then reason and experience cannot reach God. To know anything about God, you need access from God’s side — a disclosure from the divine to the human. This is revelation. And the moment revelation enters as a source of knowledge, the question of its relationship to reason — which operates on completely different grounds — becomes unavoidable.

1. Why the Simple Scheme Failed

The initial answer to the faith-reason problem seemed obvious enough: use reason for questions about this world, and use faith (trust in revealed authority) for questions about God and the next world. This was the simple scheme. And it collapsed almost immediately, because it generated problems that it had no resources to solve.

Problem One — Conflicting Revelations

The premise of the scheme is that revelation is authoritative. But multiple people had been recognised as channels of revelation: Saint John, Saint Paul, Francis of Assisi, and many others had all received divine experience and communicated what they received. The Church had officially recognised the teachings of all of these figures.

What happens, then, when these authoritative sources disagree with each other on the same question? Which authority do you follow? And on what basis do you decide? That decision — choosing between two conflicting authorities — cannot itself be made on the basis of revelation (which is the very thing in dispute). It requires a judgment. And making a judgment requires some standard by which to judge. Where does that standard come from?

Problem Two — Ambiguity of Language

Revelation was recorded in specific human languages: Hebrew, Aramaic, Greek, and Latin. These languages, like all human languages, are inherently imprecise. Words carry multiple meanings; the same sentence can be read in different ways; translation introduces further ambiguity. When the meaning of a revealed text is unclear, how is it to be clarified? Again, the clarification cannot come from revelation itself (the text is precisely what is unclear). It must come from interpretation — a rational activity.

Problem Three — Gaps in Revelation

Revelation does not cover everything. Large areas of human life — commerce, law, political administration, medicine, science — receive no direct guidance from scripture. The faith-reason scheme says: use reason for this world. But how do you know when a question is a ‘this world’ question and when it is an ‘other world’ question? Drawing that line requires a judgment — which again is a rational activity — and that judgment can itself become the subject of disagreement.

Problem Four — Disputes Between Faith and Reason

Sometimes reason arrived at conclusions that appeared to conflict with what faith taught. When this happened, which took priority? The scheme says ‘reason for this world, faith for the other world’ — but a conflict between the two presupposes that the same question is being addressed from both directions at once. Who settles that dispute? Reason cannot settle it, because faith is an independent authority. Faith cannot settle it, because that would simply be asserting its own priority without argument. The problem is circular.

These four problems are not edge cases or unusual difficulties. They are structural features of any model in which God and the world are separate and revelation is therefore necessary. The faith-reason controversy is not a medieval failure to think clearly — it is the inevitable consequence of the model. And understanding that it is inevitable is the first step toward understanding why medieval thinkers struggled with it so persistently and so seriously.

2. Why Revelation Is Necessary — and Why It Cannot Be Verified

To understand why faith is not optional in the Christian model, it helps to understand the structural necessity of revelation — and why revelation, by its nature, cannot be verified by ordinary rational means.

The Room Analogy

Two rooms: Imagine you are standing in one room. God is in the next room. And there is no door — you cannot enter the room where God is. Now someone comes from that room and tells you about it. He describes what is in there, what God is like, what God wants. You have no way of checking whether he is telling the truth. You cannot enter the room yourself. You cannot verify his account. You must either trust him or not. This is the structural situation of the human being in relation to God in the Christian model. God is in a different ontological ‘room’ — a realm of infinite reality that finite creatures cannot enter. Revelation is the account given by those who have somehow received access. And faith is the trust in that account.

Why These Claims Cannot Be Verified by Repetition

Scientific claims can be verified by repetition. Newton’s third law of motion — every action has an equal and opposite reaction — can be tested by any person at any time. Release a balloon with air in it and observe the direction of the balloon versus the direction of the escaping air. Repeat as many times as you wish. The claim is confirmed every time. This is what makes scientific claims reliable in the specifically scientific sense: they can be reproduced, tested, and in principle falsified.

Christian claims are of a completely different kind. They are historical: they concern specific events that happened at specific times in the past. Jesus was born at a particular moment in history. He taught, was crucified, and rose from the dead — all at specific historical moments, in specific places, involving specific people. These events cannot be reproduced. You cannot arrange a re-run of the Crucifixion to see if the same result occurs. Historical events are by definition unrepeatable. And what cannot be repeated cannot be verified in the scientific sense.

The Newton comparison: Newton says: ‘Every action has an equal and opposite reaction.’ You test this with a balloon. It works. You test it with a rocket. It works in space, in vacuum, everywhere. The claim is confirmed repeatedly by anyone who tests it. Now compare: ‘Jesus rose from the dead.’ You cannot arrange a test. You cannot repeat the event. The only basis for accepting the claim is the testimony of those who witnessed it — which requires trust. That trust is faith.

This does not mean Christian claims are false — it means they belong to a different epistemic category than scientific claims. Faith is not a defective or immature version of scientific knowledge; it is the appropriate response to a kind of claim that cannot be verified by repetition. The structural situation of the Christian believer — unable to verify revealed claims by their own investigation, required to trust revealed authority — is not a contingent limitation. It follows necessarily from the model of God and world as completely separate.

And where faith is structurally necessary, the question of its relationship to reason is also structurally necessary. This is the faith-reason controversy in its deepest form.

3. The Spectrum of Responses — Five Positions

Medieval thinkers did not arrive at a single answer to the faith-reason controversy. Instead, a spectrum of positions emerged — ranging from those who gave reason near-total authority to those who rejected reason almost entirely. The following table maps the major positions:

The movement across this spectrum is not random. It reflects the lessons of experience. Eriugena and Abelard showed what happens when reason is given too much authority. Bernard showed what happens when reason is rejected too completely. Each extreme demonstrated its own inadequacy. The search for a workable middle position — one that takes both faith and reason seriously, assigns each its proper domain, and does not let either swallow the other — is the central intellectual project of medieval philosophy from the eleventh century onward.

This lecture focuses on the two extreme failures — Eriugena’s rationalism and Bernard’s anti-rationalism — and on Abelard’s important but ultimately incomplete attempt at a middle path. The successful synthesis — Anselm’s formula and Aquinas’s architecture — belongs to the lectures that follow.

4. Eriugena — When Reason Contradicts Faith

We have already studied Eriugena’s philosophical system in detail. For the faith-reason controversy, the important point is not what he concluded but what his approach revealed about the relationship between reason and faith.

Eriugena was utterly confident that reason and faith cannot conflict. His argument was simple: both reason and revelation flow from the same divine source — God. God is the creator of the rational order and the author of revelation. Since God is perfectly consistent, his two self-disclosures — through the rational structure of reality and through revealed scripture — cannot contradict each other. Any apparent contradiction is simply a failure of our understanding, not a genuine conflict.

Eriugena’s own words: ‘There is no doubt that reason and authority both flow from one fountain, namely divine wisdom. Consequently no authority should frighten you away from these things, which the rational persuasion of right contemplation firmly teaches. For true authority does not oppose right reason, nor right reason true authority.’

This is philosophically attractive. If reason and faith both come from God, then following reason faithfully should lead you closer to faith, not away from it. The two should converge. But what actually happened?

Eriugena followed his philosophical reasoning with complete rigour and arrived at pantheism — the conclusion that God and the world are not genuinely distinct, that all things dissolve into the divine unity. This is precisely the conclusion that orthodox Christianity most firmly rejects. It denies the distinction between creator and creature; it makes sin and evil unreal; it eliminates personal survival after death; it collapses institutional theology into private mysticism.

The lesson was sobering. Following reason faithfully — starting from perfectly reasonable premises within the Christian tradition — did not lead to confirmation of Christian teaching. It led to contradiction of it. Eriugena’s own career demonstrated that the claim ‘reason and faith do not conflict’ is not a principle that reason can always vindicate in practice.

Moreover — and this is philosophically significant — Eriugena was honest enough to say where he would have to choose if forced. He wrote: ‘We should follow reason, which investigates the truth of things, and is overpowered by no authority.’ And: ‘Reason is prior in nature, but authority in time.’ In other words, when forced to choose, reason would win. Pressed to its logical conclusion, this position is incompatible with the fundamental presuppositions of medieval Christian philosophy — that scripture is the revealed word of God and that the Church’s interpretation of it is definitive and binding.

5. Saint Bernard of Clairvaux — When Faith Abandons Reason

Saint Bernard of Clairvaux (1091–1153) represents the opposite extreme: a deep suspicion of reason, a conviction that mystical experience is the only reliable path to God, and a fierce opposition to anyone who thought otherwise.

Bernard joined the Cistercian Order in 1122 and became abbot of Clairvaux in 1125. He was one of the most powerful personalities of the twelfth century — a maker and breaker of popes, a driving force behind the Crusades, a vigorous opponent of corruption within the Church. His mysticism was not contemplative passivity; it was intense, active, and demanding.

Bernard’s Theological Vision

Bernard held that this life is simultaneously a test of Christian faith and a punishment for Adam’s sin. Humanity, cast out of its true home by Adam’s prideful rebellion, wanders through a dark world in desperate need of God’s grace. We cannot save ourselves; we are entirely dependent on God. The road home is not through learning and scholarship — it is through humility, love, and the direct gift of divine grace.

Bernard was not merely theorising. He claimed — and there is no reason to doubt his sincerity — that he had personally experienced God’s presence, not once but many times. His description of this experience is among the most remarkable in medieval literature:

Bernard’s mystical experience: ‘The Word has visited me and that many times. And though he has often entered into me I have never known when he came. I have felt his presence, I remember that he has been present, and sometimes I have been able to foretell his entrance, but never to perceive his coming or his going. He did not enter by the eyes, for he is without colour, nor by the ears, for he is without sound… How then did he enter? Only by the movement of my heart have I been aware of him. In the flight of vices and the restraint of carnal affections I have perceived the power of his virtue… And as I have reflected on all these things I have been overwhelmed by his greatness.’

This experience — felt directly, immediately, without the mediation of argument or scholarship — was for Bernard the only genuine access to God. It could not be philosophically justified; it needed no justification. ‘I believe though I do not comprehend, and I hold by faith what I cannot grasp with the mind.’ Humility and love prepare the soul for this encounter; pride and intellectual ambition close it off.

Bernard’s Critique of Abelard

Bernard’s opposition to Abelard was therefore not merely personal or political. It was a clash of philosophical principles. In his view, Abelard had committed two connected errors.

The first was intellectual pride. Abelard was not simply curious — he was, Bernard thought, arrogant. He displayed his ability to defeat opponents in argument, set up rival schools, attracted students away from their teachers, and engaged with theology as if it were just another subject for logical analysis. This pride was, in Bernard’s framework, the most dangerous spiritual disposition — the same pride that caused Adam’s fall.

The second error was the book Sic et Non. Peter Abelard had written a book whose title means ‘Yes and No.’ In it, he collected more than 158 questions on which authoritative Church fathers had given contradictory answers. Saint Augustine says one thing; Saint Jerome says another. The same theological question — addressed by multiple revered authorities — received opposite answers. Abelard’s stated purpose was to train students in the discipline of logical analysis: here are real contradictions; work through them; develop your capacity for rigorous thinking. He did not intend to undermine faith — he quoted with evident approval the principle that ‘by doubting, we question; by questioning, we reach truth.’

Bernard’s response: the stated purpose is irrelevant. Young and impressionable minds cannot safely encounter the fact that the Church’s greatest fathers contradicted each other on fundamental questions. Confronting students with 158 contradictions in Church teaching is not intellectual training — it is a threat to their faith, however benign the teacher’s intention. And damaged faith cannot be fixed by the same reason that damaged it.

Bernard’s position stated sharply: The real criminal is not Abelard the individual — it is reason itself, with its insatiable appetite for proof and evidence. Once you enter the ‘rational road,’ there is no natural stopping point before heresy and damnation. The solution is not to reason more carefully; it is to refuse to enter the road at all.

Bernard’s Mystical Union — The Absorption Metaphors

Bernard describes the soul’s union with God through a series of vivid images — all of which, interestingly, carry Neoplatonic echoes:

Three metaphors for mystical absorption: A tiny drop of water falling into a large quantity of wine — it seems to disappear, taking on the wine’s colour and taste. Iron heated in fire until it glows incandescent — it loses its original form, becoming radiant with the fire’s quality. Air inundated by sunlight — it seems transformed into light itself, becoming not merely illuminated but itself a source of illumination.

In all three cases, the lesser substance is absorbed into the greater. The soul, in mystical union with God, undergoes a transformation of this kind — not annihilated, but so thoroughly permeated by the divine that it loses its merely human character.

Bernard was right not to press for a rational analysis of this experience. As the Neoplatonic background of his metaphors suggests, any attempt to explain this union philosophically — to ask what it means for the soul to ‘become’ divine — leads directly toward Eriugena’s conclusions and thence toward the pantheism the Church condemned. The mystical experience is real and genuine. The rational explanation of it is dangerous. Better to feel it and be silent about its metaphysical implications.

The Fatal Contradiction — Even Bernard Could Not Escape Reason

Bernard’s anti-rationalism contained an internal contradiction that he could not resolve. His position was that reason should be abandoned in favour of mystical experience. But communicating this position — explaining it, defending it, persuading others of it, using it to demolish Abelard in argument — required exactly the faculty he was trying to abandon.

The inescapability of reason: Suppose Bernard tells someone: ‘You should not use reason — it leads to heresy.’ The person responds: ‘Why not?’ Bernard must now give reasons. He must explain why reason is dangerous, argue that mystical experience is more reliable, demonstrate that Abelard’s rationalism led to bad conclusions. Each of these moves is itself a rational move — an appeal to evidence, an argument from observed consequences, a claim that one approach is better than another for specifiable reasons. The moment Bernard opens his mouth to argue against reason, he is using reason.

Bernard spent enormous energy arguing, writing, preaching, and persuading — all of which are rational activities. His career as a public intellectual was built on his ability to make compelling arguments. He was one of the most effective polemicists of the twelfth century precisely because his arguments were forceful and his logic was clear. And yet his doctrine said that all of this was useless and dangerous.

This is not a minor inconsistency. It is a fundamental problem with the anti-rationalist position. Reason cannot be completely abandoned — not in practice, not even in theory, because even the theory that reason should be abandoned must itself be stated and defended using rational means. The question is not whether to use reason, but how much, for what purposes, and within what limits.

6. Peter Abelard — Reason, Questioning, and Faith

Peter Abelard, whom we discussed at length in the previous lecture on universals, represents a third approach: neither the wholesale embrace of reason that characterised Eriugena, nor the wholesale rejection of reason that characterised Bernard, but the attempt to use reason in the service of a deeper and more genuine faith.

Two Kinds of Faith — A Helpful Way to Understand Abelard

The following distinction is not a concept proposed by Abelard himself. It is a modern explanatory framework that helps illustrate the kind of faith Abelard seems to encourage.

Using the explanatory framework introduced above, Abelard’s thought aligns more closely with what we have called examined faith than inherited faith. He does not dismiss inherited belief as worthless—faith received through family and tradition can be sincere and meaningful. However, Abelard argues that faith should not remain unexamined. It ought to be strengthened through questioning, rational inquiry, and understanding. In this sense, genuine faith is not faith that fears reason, but faith that has been refined and deepened through it.

Abelard’s principle: ‘By doubting we question, and by questioning we reach truth.’ This is not scepticism — it is method. Doubt is not the enemy of faith; it is the gateway through which faith becomes genuine rather than merely inherited.

Sic et Non — Yes and No

The most famous — and most controversial — product of Abelard’s approach was his book Sic et Non, which means ‘Yes and No.’ In it, he compiled a list of more than 158 theological questions and, for each question, set out the conflicting answers given by authoritative Church fathers. On this question, Augustine says yes; Ambrose says no. On that question, Jerome takes one position; Gregory takes the opposite.

The book did not offer Abelard’s own resolutions. It presented the contradictions and left them open, inviting students to work through them. Abelard’s stated aim was intellectual training: genuine faith requires genuine understanding, and genuine understanding requires the capacity to engage with difficult and conflicting material. If students are going to defend the faith against non-Christians and heretics, they need logical tools. Sic et Non was meant to sharpen those tools.

Abelard’s logic of doubt: ‘By doubting, we question; by questioning, we reach truth.’ Doubt is not the end of faith — it is the engine of understanding. A faith that cannot survive questioning is not a mature faith but a fragile one. Abelard wanted to help his students build a faith robust enough to withstand serious intellectual challenge.

Bernard’s response, as we have seen, was that the book was criminally irresponsible. Young minds cannot safely encounter 158 contradictions in Church teaching. The exposure would damage faith, not strengthen it. And even if Abelard meant no harm — which Bernard doubted — the effect on vulnerable students was the same regardless of intention.

Abelard on Intention and Genuine Morality

Abelard’s approach to faith had implications for ethics as well. He held that morality is not about blind obedience to rules — it is about intention and genuine understanding. God does not look only at what we do; God looks at what we mean when we do it.

This view rested on a specific reading of a specific moment in the Gospels. When Jesus was being crucified — tortured, mocked, surrounded by enemies — he prayed: ‘Father, forgive them, for they know not what they do.’ The Roman soldiers who were carrying out the execution were following orders from their commanders. They had no personal enmity toward Jesus. They were doing what they had been told was right and proper to do. Their action was harmful; their intention was not malicious. And Jesus, from the cross, asked God to forgive them on precisely these grounds: they did not understand what they were doing.

For Abelard, this moment in the Gospels revealed something fundamental about the nature of sin, morality, and God’s judgment. Sin is not merely the performance of a forbidden action. Sin requires understanding and intention. A person who does something genuinely harmful while genuinely believing they are doing right — whose intention is good, even if their action has bad consequences — is in a different moral position than a person who acts badly knowing it to be bad.

This also explains why examined faith matters morally. If you follow religious rules without understanding them — if your obedience is purely mechanical, purely habitual, without any genuine comprehension of what you are doing and why — then your morality is not fully formed. You are following correctly, perhaps; but you are not acting from genuine goodness, because genuine goodness requires understanding. God sees not only the action but the heart. And a heart that has not genuinely engaged with what it believes has not yet become fully responsible for what it does.

Abelard’s Strong Commitment to Faith

It would be a mistake to read Abelard as someone who secretly preferred reason to faith. He was explicit and emphatic in his commitment to Christian belief. In one of his most direct statements, he wrote: ‘If to be a philosopher means denying Saint Paul, I do not want to be a philosopher.’ And elsewhere: ‘If becoming Aristotle means moving away from Jesus, I do not want to be Aristotle.’

These are not defensive concessions made under pressure. They reflect a genuine and deep personal faith. Abelard used reason in the service of faith, not instead of it. He believed — as Eriugena had before him — that reason and faith are not ultimately opposed. But unlike Eriugena, he did not let reason run unchecked to its logical conclusions regardless of where they led. When reason led him into conflict with the Church, he did not resolve the conflict by simply following reason further. He acknowledged the conflict and accepted its consequences — including repeated condemnations.

7. The Double Dead End — Why Neither Extreme Can Succeed

The experience of Eriugena, Bernard, and Abelard together reveals a structural double impossibility: following reason all the way leads to results faith cannot accept; abandoning reason entirely is not actually achievable. Every attempt at one extreme or the other demonstrated the need for something different.

The conclusion that emerges from this double failure is not that the faith-reason question is unanswerable. It is that both extremes are wrong, and a middle path must be found. The question is: what does that middle path look like? What are its principles? Where does it draw the line between the domain of reason and the domain of faith? And how does it prevent reason from expanding indefinitely (the danger of Eriugena and Abelard) while also preventing the abandonment of reason from making theological discourse impossible (the danger of Bernard)?

These are the questions that Saint Anselm of Canterbury would begin to answer in the eleventh century — and that Thomas Aquinas would answer most completely in the thirteenth. Their approach represents neither Eriugena’s rationalism nor Bernard’s anti-rationalism, but a genuine synthesis in which faith and reason each have their proper domain and neither undermines the other.

8. The Modern Relevance — The Controversy Has Not Ended

The faith-reason controversy is not merely a medieval problem. It is alive today in concrete, recognisable forms. Any sincere and thoughtful religious believer who is also scientifically literate faces a version of the same tension that exercised the medieval thinkers.

• The age of the universe: Science holds that the universe is approximately 13.8 billion years old, and the Earth approximately 4 to 5 billion years old. A traditional reading of the Bible places the age of the Earth at roughly 6,000 years. These are not marginally different estimates — they differ by a factor of nearly a million.
• Human origins: The theory of evolution holds that human beings evolved from earlier primate ancestors over millions of years through a process of natural selection. The Book of Genesis describes God creating human beings from the dust of the ground. These are not obviously reconcilable accounts without significant reinterpretation of one or the other.
• The motion of the Earth: The Bible describes the sun as moving — and this was the reading that brought Galileo into conflict with the Church when he argued, correctly, that the Earth moves around the sun and not vice versa. The Church’s insistence on a literal reading of scripture in the face of astronomical evidence is the most famous historical instance of faith-reason conflict.

In each case, the question that a sincere religious scientist must face is the same one that medieval thinkers faced: when scripture and observed evidence conflict, which takes precedence? And if the answer is always ‘scripture,’ then much of what modern science has established must be rejected. If the answer is always ‘science,’ then much of what scripture teaches must be reinterpreted until it means something quite different from what it plainly says.

This is not a problem that was invented in the medieval period and should have been solved by now. It is a structural feature of any religious tradition that rests on revealed texts and is also engaged with rational enquiry into the natural world. The medieval thinkers were not backward for struggling with it — they were honest about a genuine difficulty that every subsequent generation of thoughtful believers has had to face again.

It is worth noting that some of the greatest scientists of the modern period were also committed Christians. Isaac Newton — whose laws of motion and gravitational theory constitute one of the greatest achievements of human reason — was a deeply serious student of theology. Gottfried Wilhelm Leibniz — one of the most original minds in the history of philosophy and mathematics — was also a committed Christian. The compatibility of scientific brilliance with religious faith is not a paradox to be explained away; it is a historical fact that the faith-reason controversy does not make impossible.

Conclusion — The Necessity of Compromise

The faith-reason controversy is not a controversy that could have been avoided. It is the necessary consequence of the Christian model — in which God and the world are completely separate, revelation is therefore necessary, and the revealed content cannot be verified by the ordinary methods of rational enquiry. Once revelation enters as a source of knowledge, the question of its relationship to reason becomes inescapable.

The two extreme responses to this inescapability both failed in instructive ways. Eriugena’s confident rationalism led to pantheism — proving that following reason faithfully, even from Christian premises, can lead to conclusions that contradict Christian teaching. Bernard’s confident anti-rationalism proved unliveable — demonstrating that reason cannot be completely abandoned, because even the rejection of reason must be communicated and defended by rational means.

Abelard made the most sincere and philosophically serious attempt at a middle path: examined faith, the use of reason to understand and deepen belief rather than to replace it. His distinction between inherited and examined faith is philosophically important and remains relevant. But his own career demonstrated that sincerity of intention and philosophical seriousness are not sufficient to solve the structural problem. Sic et Non, however pedagogically sound, generated consequences that the medieval framework could not absorb. The successful compromise — the one that would define the intellectual architecture of high medieval philosophy — required a more systematic answer: a clear account of what reason can reach on its own, what revelation alone can provide, and where the two overlap. That answer was provided by Saint Anselm of Canterbury, whose formula ‘I believe in order to understand’ captures in six words an entire programme of philosophical theology — and whose famous argument for God’s existence would put his approach to the test in the most demanding way possible.

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