QuestionsWhat makes something right?One can be good without believing in God
What makes something right?Nature or conscience

One can be good without believing in God

Denis Diderot 1713 · 1784Gather all human knowledge in the Encyclopédie.
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What it claims

Good conduct does not depend on faith: an unbeliever can be an honest person, and a believer may not be.

Why

We can love doing good by inclination and upbringing, and experience shows that honesty makes us happier in this world.

In short

"One can be good without believing in God" is an argument by Denis Diderot (Conversation with the Maréchale, c. 1774) on the question "What makes something right?" (answer: nature or conscience). Its claim: Good conduct does not depend on faith: an unbeliever can be an honest person, and a believer may not be. According to AskPhilosophy's logic check (Z3 solver), the argument is valid only if one grants a premise the author leaves unstated (P3). AskPhilosophy presents 3 objections, 2 of them with a documented reply, and the original text behind each premise, checked word for word.

Conversation with the Maréchale, c. 1774
Valid with an implicit premise

A very devout maréchale is surprised: a philosopher who believes in nothing, and yet neither steals nor kills? What motive can an unbeliever have to be good? The philosopher, "Crudeli", Diderot's mask, answers that goodness has roots other than the fear of hell.

P1One can be born taking pleasure in doing good, and a good education strengthens this inclination.
P2Experience shows that, for one's happiness in this world, it is better to be honest than a rogue.
P3 · implicit premiseThese this-worldly motives can be enough to make someone honest, without hope of reward or fear of punishment after death.
P4And believing is not enough to act well: people believe, and every day behave as if they did not. Religion has almost no real influence on morals.
Therefore good conduct does not depend on faith: an unbeliever can be an honest person, and a believer may not be.

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 P3, the computer finds a case where someone has a good inclination, a good education and an interest in being honest, but where this is not enough without fear of the afterlife: the unbeliever would then not be honest.
Valid with P3. The conclusion has two parts: P1, P2 and P3 show that faith is not necessary to be honest; P4 shows that it is not sufficient. Without P3, one can still say, like the maréchale, that these motives are too weak when temptation is strong. On the factual side, the weak point is P4: Crudeli relies on examples ("this example, and a hundred thousand others"), not on a survey. And the argument shows that an unbeliever can be honest, not what makes an action good: that is Dostoevsky's objection.
Analogy. A student can work without fearing punishment: because he likes the subject, because he was raised to, because he sees it helps him. Conversely, fear of punishment has never stopped everyone from cheating.

Objections

3

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

T
The maréchale (in the dialogue) attacks premise 4

Granted. But what harm would there be in having one more reason to do good, religion, and one less reason to do evil? Fear of God holds back at least some people.

Diderot replies
Diderot In the dialogue
Temptation is too near, and hell too far. If we want honest people, good laws work better: tie each person's interest to the common good and reward virtue as we punish crime.
Locke 1689 · attacks premise 3

An atheist cannot be bound by his promises, contracts and oaths, which are the bonds of society: he fears no judge above him. That is why atheists should not be tolerated.

Diderot replies
Diderot Diderot in 1746, still a deist: a partly agreeing answer
The deist has more motives to be virtuous than the sceptic, and the sceptic has one more than the atheist. But the atheist's honesty still has three supports: fear of the law, his temperament, and the knowledge of the advantages virtue brings in this life. Without them, it would lack a foundation.
D
Dostoevsky (The Brothers Karamazov) 1880 · attacks the conclusion

Showing that unbelievers behave well does not say what makes an action good. Without God, morality is just an inclination or a calculation: if someone has neither that inclination nor that interest, nothing obliges him. The novel's idea is summed up by a famous formula: "if God does not exist, everything is permitted" (a summary of Ivan's words, not an exact sentence of the book).

no reply
summary: their text is not yet in our corpus
No reply possible: objection raised in 1880, after the author's death (1784).
What today's voices say
Defend it
Neil deGrasse TysonHe says the assumption that one has to be religious to be moral is false, and 'empirically false', as shown by largely secular countries.