This letter comes from a doctoral student and professor in a seminary in Spain.


Amongst our small faculty there is discussion concerning the relationship between natural law, the Ten Commandments, and the issue of the Sabbath.  It is my understanding that the Ten Commandments are a summary of the natural moral law.  However, we know that since the resurrection of Jesus, the “holy day” has changed from Saturday to Sunday.  My questions are the following: If the Ten Commandments summarize natural law, then what day does the natural man “know” to be the day of rest/worship?  Or has natural law itself changed with the coming of Christ?  Do you personally exclude Sabbath worship from natural law?


Thank you for writing.  Here is how I understand the matter.  (By the way, my favorite saint discusses all these things in much greater detail in Summa Theologiae, I-II, Questions 98-108.)

Old Testament law contains several different kinds of precept:  Moral precepts, such as the prohibition of murder; ceremonial precepts, such as the prohibition of mixing different kinds of fibers in the same garment; and judicial precepts, such as the rules about how many witnesses are necessary to convict someone of a crime.

All of the moral precepts of the Old Testament law coincide with the natural law.  They would have been knowable by reason alone, even apart from divine revelation; they bind universally and without exception; and they cannot be changed.  The ceremonial elements in Old Testament law could not have been worked out by reason alone, so they depend on divine revelation.  Although they held for the people of the old covenant, they do not hold universally, and they can be changed by divine authority.

If taken not just in their words, but together with what they imply, suggest, and presuppose, the moral precepts of the Ten Commandments do summarize the natural law.  For example, the commandment against adultery presupposes the institution of marriage, which is the unique setting for the practice of the sexual powers.  Although it explicitly prohibits only one form of sexual impurity, this has always been understood as a placeholder, or metonymy, for all sexual impurity is wrong, but adultery is the most conspicuous example.

The fact that the moral precepts of the Ten Commandments summarize the natural law does not imply that everything in the Ten Commandments is a moral precept.  For example, we can analyze the commandment about the Sabbath into two elements, one moral, the other ceremonial.  The moral element is that times and places be set aside for remission of labor and worship of God; this is a part of the natural law, and everyone should do it.  The ceremonial element is that one of the times to be set aside be the seventh day; this command, which is not part of the natural law, was given to the old covenant community, but the Church by God’s guidance can make different arrangements for the new covenant community.

As indeed He has, for in the new covenant community we rest and worship not on the seventh day, to commemorate God’s rest from the original creation, but on the first, to commemorate the new creation which was inaugurated with the resurrection of Jesus Christ.