In several of your books you touch on the relation of the classical natural law tradition to the Ten Commandments. I have a question: Is there any tradition of connecting natural law not to the Ten Commandments, but to the Noachide commandments discussed in Jewish tradition? I ask you this question because I cannot seem to buy into the belief that Sabbath commandment is fulfilled by the Christian Sunday.
I think you are asking at least four questions (each of them interesting). What is the relation of natural law to the Decalogue, or Ten Commandments? Does the Sunday observance of Christians fulfill the commandment about the day of rest? Is that commandment part of the natural law too? Finally, could it be said that the natural law bears a similar relation to what rabbinical tradition calls the Seven Commandments Given to the Sons of Noah? Let’s take these in order.
As to the first question: Provided that they are properly understood, the Ten Commandments are a superlative summary of the general precepts of natural law -- of the unchangeable principles of right and wrong of which even a person who has never heard of the Christian faith should be aware. By “properly understood,” I mean two things. First, only the moral parts of the Ten Commandments can reasonably be said to belong to the natural law; certain other parts belong to the divine ceremonial law of the Jews. Second, each of the Ten Commandments must be read broadly; for example, the commandment against theft is to be viewed as prohibiting all injury to another person in his property, theft being merely a particularly conspicuous example. This is a “metonymy,” a figure of speech in which a part represents a whole.
As to the second and third questions: The moral part of the commandment concerning the day of rest is that times and places should be set aside for worship of God and remission of labor. Yes, this is a part of the natural law, so it applies to everyone and cannot be changed. However, the instruction to which says this must be done on the seventh day is a part of divine ceremonial law, which can be changed. True, it cannot be changed by anyone, but as we find in recorded in Matthew 16:17-19, Christ gave the Church the authority to “bind and loose.” This is why Christians have always believed that Sunday observance fulfills the commandment for them.
As to the fourth question: According to Jewish oral tradition, after Noah’s family emerged from the ark, the “sons of Noah” – this expression means the descendants of Noah, which includes not just Jews but everyone now living -- were given seven commandments. These seven, which go beyond what is actually written in the Genesis story of the flood, are usually stated like this:
1. There must be courts (this is a metonymy, representing provision for the administration of justice).
2. There must be no idolatry.
3. There must be no blasphemy.
4. There must be no incest (this is another metonymy, representing sexual immorality in general).
5. There must be no bloodshed.
6. There must be no theft.
7. There must be no eating of flesh torn from living animals.
Yes, just as you suggested, when read broadly the Noachide Commandments are sometimes considered another summary of natural law. However, the Decalogue is more complete. You were concerned about the Decalogue just because of the Commandment about the day of rest and worship, but as we have seen, we can dispose of that fear by distinguishing between the moral and ceremonial aspects of the Decalogue.
If you would like more detail about the Decalogue as a summary of natural law, you’re in luck. Open up the Companion to the Commentary and read pages 221-225. For connections with the New Testament, read the next few pages too. There is more, but perhaps that will do for starters.