One law for Rome and for Athens

Cicero 106 BC · 43 BCTrue law is right reason in agreement with nature.

What it claims

True law is one and eternal: the same at Rome and at Athens, today and tomorrow, and neither the Senate nor the people can release us from it.

Why

True law is the reason nature gave to all; if justice depended on votes, a vote could make theft just.

In short

"One law for Rome and for Athens" is an argument by Cicero (On the Laws, I, 18-43; On the Republic, III, 33) on the question "What is a just society?" (answer: one humanity). Its claim: True law is one and eternal: the same at Rome and at Athens, today and tomorrow, and neither the Senate nor the people can release us from it. 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, 1 of them with a documented reply, and the original text behind each premise, checked word for word.

On the Laws, I, 18-43; On the Republic, III, 33

Valid with an implicit premise

Is a law just simply because a people voted for it? Cicero says no. True law is not written by a parliament: it is right reason, which nature has given to all human beings. So it is the same everywhere and always, and no vote can release us from it. This idea of natural law, one law for all peoples, runs through Aquinas, Grotius, Locke and the declarations of rights.

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 is reason, everyone has reason, votes do not make what is just, and yet the just law is not the same at Rome and at Athens.

Valid with P4. P1 and P2 say what law is and that everyone has it. P3 rules out the rival thesis: justice does not come from votes. But P4 is still needed to conclude that the law is the same everywhere: a shared reason could very well call for different rules in different countries. That is the point Montesquieu would raise. Cicero himself distinguishes this "true law" from the written laws of cities, which he calls law only "to speak as the people do".

Analogy. A majority of the class votes that 2 + 2 = 5. The vote took place, but the sum is still wrong, in Paris as in Tokyo. For Cicero, what is just is like arithmetic: a vote can recognise it or betray it, not manufacture it.

Objections

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

Carneades (Rome, 155 BC) 155 BC · attacks premise 1

There is no natural right. People gave themselves laws for their own advantage: they vary between peoples and change over time. The proof: the Romans themselves built their empire by taking what belonged to others. If they wanted to be just, they would have to give everything back and return to their huts.

Cicéron replies

Cicéron

If justice consists in obeying written laws and everything is measured by utility, then whoever thinks he will gain by it will neglect the laws and break them if he can. A justice founded on one interest is destroyed by another interest: there is no justice at all, if it is not in nature.

The debate goes on (our summary) Carneades had argued one day for justice and the next day against it, to show that anything can be defended. In On the Republic, Cicero has Philus restate his speech and Laelius refute it: Laelius's answer is what contains the definition of true law. Philus's speech is known mostly through summaries (Lactantius, Augustine). This passage of the Laws does not answer the example of the Roman empire. And a follower of Carneades would accept the consequence: if there is no justice in nature, there are only useful conventions. Cicero's argument shows that it would be useful to believe in a natural law, not that it exists.

Montesquieu (The Spirit of the Laws) 1748 · attacks premise 4

Law in general is indeed human reason. But each nation's laws must be adapted to its people, climate, customs and trade, so much so that it would be very surprising if one people's laws suited another.

no reply

No reply possible: objection raised in 1748, after the author's death (-43).

The debate goes on (our summary) The disagreement is smaller than it looks. Montesquieu accepts a reason common to all peoples, and Cicero accepts that the written laws of cities vary. They differ on how much of justice must never change. Montesquieu himself writes that before human laws there were already "possible relations of justice".

Hume (reason does not command) 1751 · attacks premise 1

Reason discovers what is true or false, but it is cold: it moves us to no action and only shows the means of reaching what we desire. What approves or blames is sentiment. A reason that by itself "commands and forbids", as Cicero would have it, is therefore impossible.

no reply

No reply possible: objection raised in 1751, after the author's death (-43).

The debate goes on (our summary) For Cicero, right reason is not a mere calculation of means: it is human nature brought to completion, which includes a natural inclination to love others ("the foundation of right", On the Laws I, 43). The debate between reason and sentiment as the source of morality is still open today.