I would like clarification on two related divine and legal terms: ius sacrum and fas. They can both be translated as "divine law", but I do not think they are the same thing. I have an idea of what they might be, but I would like confirmation or correction of my ideas. Is the following paragraph — which is not a quote from anyone but just my own thoughts — a good description of what ius sacrum and fas meant in classical antiquity?

There are two words for justice, ius and fas. Ius is justice as we commonly know it: man creates laws and ensures that they are followed. Breaking ius is a matter between mortals. Fas is divine justice: gods decide what is right and they punish those who break it. Fas also describes days suitable for various affairs. I might call pietas "doing what fas requires". In this sense ius is "human law" and fas is "divine law". Of course it was in the interest of the society to avoid the wrath of gods (whether out of true spirituality or as a political tool), so people were interested in making sure fas was followed. This is what ius sacrum is for: it is man-made law concerning religion. Fas is "law made by gods about human behaviour" and ius sacrum is "law made by humans about maintaining human–god relations". They are "divine law" in very different ways.

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    Great question: note that there are at least 20 occurrences of "ius fasque," almost half from Livy, so the two certainly have an intersection of reference, if not meaning.
    – brianpck
    Nov 17, 2016 at 12:54
  • Related publication (Fr): jstor.org/stable/43844186?seq=1#page_scan_tab_contents
    – Luc
    Nov 18, 2016 at 11:37
  • It seems as if "ius" refers to a law, described by "sacram" to be sacred, but "fas" can also mean what is moral or allowed. I would answer this, but I'm not too sure about how the Latins would ever use the two or if they are interchangeable. Feb 6, 2017 at 15:31
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    Great question! This distinction was good to learn.
    – ktm5124
    Apr 18, 2017 at 6:06

1 Answer 1


Recent research has shed some new light on this question. A dissertation that came out of Rutgers in 2007 called the whole idea of ius sacrum into question.

Johnson takes a look at the evidence behind the standard interpretation. For reference, for years everyone relied on Adolf Berger's article in the RE and, later, his entry in Encyclopedia Dictionary of Roman Law, which I produce below:

Ius Sacrum. Strictly connected with ius divinum and ius pontificum. It embraces the legal principles and institutions which are connected with the relations of men to gods, with questions of cult, sacrifices, temples, consecrations, graves, and sacerdotal functions, whenever they may occur. The jurists Servius Sulpicius and Trebatius wrote on the subject of the ius sacrum. In oldest times the ius sacrum exercised a considerable influence on private law, the knowledge of legal rules and their interpretation and applicability having been a monopoloy of the priests.

Problem is, the evidence behind such a reading is flimsy. I noticed this too when looking for evidence for the phrase in PHI:

Naturae iura sacra sunt etiam apud piratas.

The sacred laws of nature are also [found] among pirates.

There are so few references, that something like this thrown in is a dead giveaway that something is amiss. The ius sacrum here isn't a legal code, but simply a description of ius, it's really ius naturae, quod sacrum etiam est.

Johnson goes through the rest of the passages and cannot find either a legal or literary precedent for it. Instead, he thinks scholars have been conflating the terms ius pontificium and ius sacrorum, but there too are differences.

The ius sacrorum (attested as early as Cicero, e.g. De Domo Sup 41.1), or, perhaps, more correctly, the iura sacrorum, was a body of religious law that governed a family's sacra, holy objects, masks, penates, etc. These were the items that Romans used in conjunction with offerings to the gods, establishing a relationship between the domus and the divine. Unless I misunderstand the argument, the ius sacrorum that deal with public sacra would fall under the domain of the pontifical college, and thus part of the ius pontificium.

This latter ius is the broader one, and is encompassed by various sub-iura (e.g. ius caerimoniarum; see p. 112 for his reasons for concluding thus).

All of this so far is a type of ius gentium, man-made law that governs individual nations. The Roman implementation of the ius sacrorum or ius caerimoniarum would not necessary apply to the Greeks, Carthaginians, or Gauls. This can be contrasted though with the ius naturale, 'natural law', those laws (sacra in Seneca's opinion) which the gods gave mortals.

This is where fas and nefas come in. You don't need to make a specific law or listen to the advice of the pontifices to know that cannibalism is wrong. It's not just wrong on a technical or legal level, but morally wrong (cf. Ov. Met. 6.585). It's a broach of human nature, and the gods will not only punish you (which can happen from carelessness), but sentence you to an eternity of torture in the underworld.

As such, nefas is not legalistic, but rather laws were created to address issues of fas and nefas, not that they necessarily needed to do so.

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    Many thanks! It seems that I wasn't completely off the mark (especially with fas), but this answer really changes the way I see these concepts. It starts making sense.
    – Joonas Ilmavirta
    Apr 18, 2017 at 4:11
  • Ah, so that's where we get nefarious. I was trying to think of English derivatives of fas. Any others?
    – ktm5124
    Apr 18, 2017 at 6:03
  • @ktm5124 Not directly, but it's related to fare, so words like infant are related.
    – cmw
    Apr 18, 2017 at 6:09
  • I know it's been a while since you posted this! I'm deeply curious what the Met reference is, though - which book? And which story?
    – ariadnep
    Dec 24, 2020 at 2:16
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    @ariadnep I edited it to add the book in. It's book 6, the story of Procne, Philomela, and Tereus.
    – cmw
    Dec 27, 2020 at 0:02

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