QuestionsDoes God exist?Natural religion is perfect: revelation can add nothing to it
Does God exist?DeismMiracles and testimony

Natural religion is perfect: revelation can add nothing to it

The deists' Bible; "Christianity as old as the Creation"

Matthew Tindal 1657 · 1733Christianity is as old as the Creation: natural religion is perfect and revelation can only restate it.
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What it claims

External revelation can neither add to natural religion nor take from it: it can only republish it, and differs from it only in the way it is delivered.

Why

A perfect God gave everyone, from the beginning, a perfect law: a late revelation can only restate its content.

The same idea through history
Matthew Tindal1730Matthew Tindal, aged over seventy, publishes a dialogue between two speakers, A and B. He argues that the Gospel is "a republication of the religion of nature". The book became the reference of the English deists and drew very many replies.
Thomas Paine1794Paine takes up the same idea sixty years later: a word of God valid for all must be universal, and only Creation is.
In short

"Natural religion is perfect: revelation can add nothing to it" is an argument by Matthew Tindal (Christianity as Old as the Creation, 1730, ch. I and VI, 1730) on the question "Does God exist?" (answer: deism). Its claim: External revelation can neither add to natural religion nor take from it: it can only republish it, and differs from it only in the way it is delivered. 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 3 objections, 0 of them with a documented reply, and the original text behind each premise, checked word for word.

Christianity as Old as the Creation, 1730, ch. I and VI
Valid with an implicit premise

If God is infinitely wise and good, he wanted from the first day that all people could know what he expects of them. So he gave them a law through reason alone, and that law cannot be imperfect, because a perfect lawgiver does not make bad laws. Tindal draws a consequence: Christian revelation cannot add anything to natural religion. It can only restate it and clear away the superstitions mixed into it. For him this honours revelation: it agrees with reason, like two copies of the same contract.

P1God is infinitely wise, good and unchanging: he makes no imperfect law, and time teaches him nothing he had not foreseen from eternity.
P2Such a God wanted religion to be one and known to all. So he gave all people, at all times, sufficient means to know what he wants them to know and do, in their situation.
P3A law given to all by a perfect lawgiver is complete: nothing can be added to it or taken from it without making it imperfect. So the religion of nature is perfect.
P4 · implicit premiseIf an external revelation brought to religion a necessary duty or truth that it lacked, the religion of nature would not be complete.
Therefore external revelation can neither add to natural religion nor take from it: it can only republish it, and differs from it only in the way it is delivered.

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 computer finds a case where natural law is complete and yet a revelation brings something new: for example information of another kind, such as historical facts or a means of salvation, which is not part of natural law.
The argument is valid with the hidden premise P4. From P1 and P2, God gave everyone a sufficient law; by P3 it is complete; and P4 says a revelation that brought something new would show it is not. So the objections target P2 (was this law really accessible to all through reason alone?) and P4 (is revelation useful only if it brings a new duty?).
Analogy. A perfect contract signed by both parties, then copied before a notary, says nothing more than the original. The notary can make it more readable or more formal, but cannot add a clause without changing it. Tindal says: revelation is the copy, reason is the original.

Objections

3

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

J
John Conybeare (A Defence of Revealed Religion) 1732 · attacks premise 2

Saying that God gave a law and therefore gave means of knowing it proves nothing. What we are able to discover by reason is a law for us, and what we cannot discover is no law for us. Whether reason alone suffices for everything founded in the nature of things must therefore be settled by the facts, not assumed at the start.

no reply
We have not yet found a direct reply by Tindal in the texts.
The debate goes on (our summary) Tindal died in 1733 and his second volume never appeared; we found no direct reply to Conybeare. His book does say he asks not for equal knowledge for all but for "what is sufficient for the circumstances they are in". Conybeare replies that this clause destroys the argument: if all have sufficient means to discover the whole of natural religion, all have the means of equal knowledge.
Where the debate stands (our summary)Our summary: the point at issue is whether unaided human reason could reach all of natural religion. Deists answer from right (God must have made it possible), their opponents from facts (the history of religions, the disagreements of the wise). The debate is not settled.
Joseph Butler (The Analogy of Religion) 1736 · attacks premise 2

History shows that even the greatest minds of the pagan world doubted essential things, and that there is no ground to affirm that most people could have discovered natural religion alone, nor any probability that they would have. It is absurd to say that revelation is superfluous.

no reply
No reply possible: objection raised in 1736, after the author's death (1733).
The debate goes on (our summary) Butler writes three years after Tindal's death. A possible answer for Tindal (our reconstruction): men's having erred does not show the means were lacking (reason was at their disposal); Butler answers that this makes revelation useful, which is enough to refute the idea of a useless revelation.
Where the debate stands (our summary)Our summary: Tindal speaks of what God must have made possible; Butler speaks of what people have done in practice. Both positions can be true at once, and the debate is about what counts as a "sufficient" means.
Joseph Butler (The Analogy of Religion) 1736 · attacks premise 4

Christian revelation is indeed a republication of natural religion, but it also contains an account of a dispensation of things that reason cannot discover, from which particular duties follow. Natural religion is the foundation and principal part of Christianity, but in no sense the whole of it.

no reply
No reply possible: objection raised in 1736, after the author's death (1733).
The debate goes on (our summary) Tindal had written in advance (ch. VI) that if a revealed religion differs from natural religion in any one particular, even in the minutest circumstance, that alone ruins everything else said for it. For him, a duty that does not come from reason is an arbitrary command. Butler replies (Part II, ch. V) that the reasons of all the Christian precepts are evident, once what Christ did is known.
Where the debate stands (our summary)Our summary: everything depends on what is called religion. If it is the set of duties reason discovers, Tindal may be right; if it also includes a history of salvation that gives new duties, Butler is right. The disagreement is partly about the word, and partly about whether such a history exists.
In the same family · Miracles and testimony
Against miraclesDavid Hume
Does God exist?Agnosticism 3
The only word of God is the Creation we beholdThomas Paine · 1794
Does God exist?Deism 3