QuestionsWhat is a just society?Natural law would hold even if God did not exist
What is a just society?Natural rights

Natural law would hold even if God did not exist

Etiamsi daremus ("even if we were to grant")

Hugo Grotius 1583 · 1645Dutch jurist and thinker who grounds natural law in the sociable, rational nature of man, valid even without appeal to God.
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What it claims

Natural law would have some validity even if one granted that God does not exist or does not concern himself with human affairs.

Why

Humans are made to live in society with reason, and what follows from that is true by nature, as 2 and 2 make 4: God cannot change it.

In short

"Natural law would hold even if God did not exist" is an argument by Hugo Grotius (Grotius, On the Law of War and Peace, 1625: Prolegomena 8 and 11; I, 1, 10, 5) on the question "What is a just society?" (answer: natural rights). Its claim: Natural law would have some validity even if one granted that God does not exist or does not concern himself with human affairs. 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.

Grotius, On the Law of War and Peace, 1625: Prolegomena 8 and 11; I, 1, 10, 5
Valid with an implicit premise

Grotius wrote his great treatise in the middle of the Thirty Years' War. He wanted rules that Catholics, Protestants and even non-Christian peoples could accept. His answer: natural law flows from the nature of man, a being who desires to live in society and can judge by general principles. It is true in itself, like a mathematical truth, and God could not change it. He adds that this law would hold even if one granted, which cannot be done without the utmost wickedness, that God does not exist or does not care for human affairs. Note: Grotius is not an atheist. He states at once that God exists, that he is owed obedience, and that his will is a second source of law beside nature.

P1Man has a nature of his own: a strong desire to live in society, which alone among animals he satisfies by speech, and the faculty of knowing and acting according to general principles.
P2The maintenance of this social order, consonant with human intelligence, is the source of law properly so called: not taking what belongs to another, keeping promises, making good a wrong, punishing according to desert.
P3This law is unchangeable, even by God: just as God cannot cause that two times two should not make four, he cannot cause that what is intrinsically evil be not evil.
P4 · implicit premiseWhat follows from human nature and depends on no will, not even God's, keeps its value if one supposes, for the sake of argument, that God does not exist.
Therefore natural law would have some validity even if one granted that God does not exist or does not concern himself with human affairs.

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 world where law follows from human nature and depends on no will, but where it has the force of law only because a divine legislator orders it: then, without God, it would remain a piece of prudential advice.
The argument is valid with the hidden premise P4. P1 and P2 make law depend on human nature; P3 says its content depends on no will, even a divine one; P4 draws from this that God's existence changes nothing. The objections target P3 (for Ockham, God could command otherwise) and the step from P3 to the conclusion (for Hobbes and Pufendorf, a law binds only if it comes from a superior). Grotius for his part keeps divine law as a second source.
Analogy. The rules of geometry depend on no will: even if nobody had written them down, the angles of a triangle would still add up to the same sum. Grotius says the basic rules of life in society are of this kind: they follow from what humans are, not from an order.

Objections

4

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

W
William of Ockham (divine command theory) 1318 · attacks premise 3

For Ockham, the acts we call bad, such as theft or adultery, are bad only because God forbids them. They could even be done meritoriously if they fell under a divine command. Nothing is evil by nature above God's will.

a defender replies
see the argument
Grotius (On the Law of War and Peace) defender of the argument · 1625
Grotius replies that God's power has logical limits: it cannot make two times two not four, nor make what is intrinsically evil not evil. He adds that God himself allows himself to be judged by this standard.
Where the debate stands (our summary)Our summary: this is the old disagreement between those who make the good a decision of God (Ockham) and those who see it as something God recognises (Grotius, and Plato before him). The debate is still open.
Thomas Hobbes (Leviathan) 1651 · attacks the conclusion

For Hobbes, it is improper to call these dictates of reason "laws": they are only conclusions about what preserves and defends a person. Law, properly, is the word of him who by right has command over others. They are laws only if considered as delivered in the word of God.

a defender replies
Grotius (On the Law of War and Peace) defender of the argument · 1625 · Written before Hobbes: an anticipated answer
Grotius had already foreseen a second source of law: the free will of God, which reason tells us to obey. For him natural law holds by the nature of man, and God adds his command.
The debate goes on (our summary) Our summary: this passage does not settle everything. For Hobbes, without a lawgiver these rules are no longer laws but advice; Grotius only says they would have "a degree of validity" without God, and does not say whether they would bind in the strong sense.
Where the debate stands (our summary)Our summary: Hobbes and Grotius agree that, as commanded by God, these rules are laws in the strong sense. They differ on what they are without him: mere advice for Hobbes, rules valid by the nature of man for Grotius. The debate is still open.
S
Samuel Pufendorf (On the Law of Nature and of Nations) 1672 · attacks the conclusion

For Pufendorf, a law is a decree by which a sovereign obliges a subject to conform his actions to what he prescribes. Grotius's definition supposes that there is something just before any law: natural law would then only point it out. Pufendorf defends the idea that obligation comes from a superior, hence from God.

a defender replies
Pierre Bayle, quoted by Leibniz (Theodicy, 1710) defender of the argument · 1705 · An answer by another author, not aimed at Pufendorf (our comparison)
Bayle, taken up by Leibniz, replies that God's will extends only to the existence of things, not to their essences. God could create a man or a circle, or leave them in nothingness, but he could not produce them without their essential properties. For Bayle, there is in the essence of certain things a moral good or evil that precedes the divine decree.
Where the debate stands (our summary)Our summary: Leibniz himself puts Grotius among those for whom the rules of good and justice come before God's decrees, and judges that Pufendorf holds a different view. The debate is still open.
D
Dostoevsky (The Brothers Karamazov, Ivan's words) 1880 · attacks the conclusion

The opposite of Grotius, in a novel: for Ivan Karamazov, without God or immortality there is no virtue, and everything is permitted. The idea is discussed in the argument devoted to it: do an inclination or a sociable nature really bind someone who does not want it?

no reply
see the argument
No reply possible: objection raised in 1880, after the author's death (1645).