QuestionsShould we believe without proof?Enthusiasm is not proof: reason must judge every revelation
Should we believe without proof?No belief without evidence

Enthusiasm is not proof: reason must judge every revelation

Against enthusiasm

John Locke 1632 · 1704The mind is born a blank slate; power comes from consent.
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What it claims

Enthusiasm is not proof. Before believing it, any claimed revelation must be examined by reason, which remains our last judge and guide in everything.

Why

A strong inner conviction proves neither that an idea is true nor that it comes from God: only reason can examine it.

The same idea through history
John Locke1700Chapter 18 of the Essay (1690) sets the limits of faith and reason. Chapter 19, "Of Enthusiasm", was added by Locke to the fourth edition (1700): in it he examines those who believe themselves directly inspired.
David Hume1748Hume takes up the rule of proportioning belief to the evidence and applies it to miracles reported by witnesses.William K. Clifford1877Clifford turns this rule into a moral duty: it is wrong to believe on insufficient evidence.
In short

"Enthusiasm is not proof: reason must judge every revelation" is an argument by John Locke (Essay concerning Human Understanding, IV.18-19 (1690-1700), 1700) on the question "Should we believe without proof?" (answer: no belief without evidence). Its claim: Enthusiasm is not proof. Before believing it, any claimed revelation must be examined by reason, which remains our last judge and guide in everything. According to AskPhilosophy's logic check (Z3 solver), the argument is valid only if one grants a premise the author leaves unstated (P4). AskPhilosophy presents 4 objections, 3 of them with a documented reply, and the original text behind each premise, checked word for word.

Essay concerning Human Understanding, IV.18-19 (1690-1700)
Valid with an implicit premise

In the 17th century, some religious groups claimed that God spoke to them directly, inside their minds, without a book or reasoning: they were called "enthusiasts". Locke does not deny that God can speak to someone. He asks a different question: how does this person know the voice comes from God? He feels sure, he feels a light within. But being sure is not being right. Saint Paul was sure he was doing right when he persecuted the Christians, and he was wrong. So a claimed revelation must face reason, like any other claim, and we should believe as much as the evidence allows, no more.

P1To love truth is to give a proposition no more assurance than the proofs it rests on allow: one proportions one's assent to the evidence.
P2To believe a revelation is to assent to a proposition on the word of the one who proposes it, as coming from God. It is therefore no more certain than the fact that it really comes from God.
P3The strength of an inner conviction proves neither that the proposition is true nor that it comes from God: one can feel sure and be wrong.
P4 · implicit premiseThere are only two ways of holding that a proposition comes from God: having examined it with reason, or relying on the strength of one's conviction.
Therefore enthusiasm is not proof. Before believing it, any claimed revelation must be examined by reason, which remains our last judge and guide in everything.

click a premise to reject it

If you accept every premise, logic forces you to accept the conclusion. So the debate is about the premises.
Checked by a logic solver: the premises cannot all be true while the conclusion is false.
Without the implicit premise: Without P4, the solver finds a case where one holds a proposition to be divine without reason examining it and without relying on conviction alone (for example through a sign judged reliable without examination). The conclusion does not follow.
Valid if P4 is added, which Locke assumes without writing it in this form. P1 and P2 say that faith in a revelation is no more certain than the proof of its origin. P3 rules out conviction as proof. P4 rules out any third way. The delicate point is P4: Locke also accepts the "written Word of God" as a rule (IV.19.16), but adds that knowing whether a book is inspired is still a matter for reason (IV.18.6). What the argument does not say: that everything "above reason" is false. Locke accepts, on the contrary, that truths reason can neither prove nor refute (the resurrection of the dead, for example) may be received on revelation (IV.17.23; IV.18.7). He excludes only what is contrary to reason, and he asks that the origin be checked.
Analogy. A message arrives: "This is the bank, give me your code." The message sounds sure of itself, and it may really be from the bank. But the confident tone does not prove it. You must check where it comes from before obeying, and the higher the stakes, the more the check matters.

Objections

4

Each objection is a conversation: click to see who replies and where the debate stands.

The "enthusiasts", as Locke describes them 1700 · attacks premise 3

The light God puts in the mind needs no proof: it shows itself, like the sun at noon. To ask for proof from someone who sees the light is ridiculous.

Locke replies
Locke 1700 · Locke's reply
Strip away the images of seeing and feeling, and this comes down to saying: "I am sure because I am sure", and "my persuasion is right because it is strong".
Locke 1700 · Locke's example
St Paul believed he was doing right in persecuting the Christians, whom he thought mistaken. Yet it was he who was wrong.
Where the debate stands (our summary)Our summary: both sides agree on one fact (one can feel strongly enlightened) and differ on its value as proof. Locke sees a state of mind, not a sign of origin. Believers who receive this feeling as a gift of God answer that demanding proof from reason amounts to giving up that gift.
Blaise Pascal 1670 · attacks premise 4

Reason is weak when it wants to judge everything: its last step is to recognise what is beyond it. We also know by the heart, and faith is God felt by the heart, not by reason. Pascal writes before the Essay and does not answer Locke: his thesis is the opposite of "reason, last judge in everything".

Locke replies
see the argument
Locke Locke (written against enthusiasm, not against Pascal)
Having a strong persuasion that a proposition is true is not perceiving that it comes from God, or even that it is true.
Blaise Pascal 1670
Pascal does distinguish the "heart" from imagination: for him, faith is God felt by the heart and not by reason. He does not propose to replace reason, but to recognise that it does not ground everything.
Where the debate stands (our summary)Our summary: Locke also admits that reason starts from evident truths it does not demonstrate (IV.18.5). The disagreement is about faith: Pascal sees in the feeling of the heart a knowledge of God, while Locke does not see in it a sign that distinguishes inspiration from illusion. No common answer is accepted.
William James 1896 · attacks premise 1

A rule of thinking that would absolutely prevent us from acknowledging certain kinds of truth, if they were really there, would be an irrational rule. Demanding proof before believing can therefore shut the door on what shows itself only to someone who agrees to believe first. James is aiming at Clifford's rule, close to Locke's; he does not mention Locke in this text.

no reply
see the argument
No reply possible: objection raised in 1896, after the author's death (1704).
Where the debate stands (our summary)Our summary: everything depends on the options at stake. For James, the proportion rule holds for questions that evidence can settle; for living, forced and momentous options that it cannot settle, one may decide otherwise. Locke reserves faith for truths "above reason" only after examining their origin. Basic disagreement about what one may believe before being able to prove it.
A tension within Locke himself 1700 · attacks the conclusion

Locke sorts propositions into three classes: according to reason, above reason (the resurrection of the dead, for example, Essay IV.17.23) and contrary to reason. He accepts that what is "above reason" becomes, once revealed, the proper matter of faith (IV.18.7). Then reason no longer judges everything: faith does have a domain of its own.

Locke replies
Locke 1700 · Locke admits it
These things, beyond what our natural faculties can discover, are, when revealed, the proper matter of faith.
Locke 1700 · But he keeps a role for reason
Even then, it belongs to reason to judge whether it is really a revelation and what the words in which it is expressed mean.
Where the debate stands (our summary)Our summary: Locke does not say that reason judges the content of everything, but the origin of every revelation and its consistency with reason's own evidence. Critics think this split leaves faith more room than the slogan "last judge in everything" suggests; defenders see a coherent position.