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The Ten Commandments as natural law

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St. Thomas Aquinas, the medieval theologian known for his comprehensive summary of all the theological thought of his time (Summa Theologica), was of the opinion that the moral commandments of the Mosaic Law (as distinct from the ceremonial ones, such as not eating pork, and the civil ones, such as stoning your wife for adultery) are part of supposed natural law.[1] Whether or not such a thing as "natural law" actually exists is up for debate.

He also thought that the entire Mosaic Law is reducible to the Ten Commandments.[2] It would follow that each of the Ten Commandments can be deduced from natural law. Such a deduction is sometimes taken as evidence supporting the argument from morality.

In this article, we examine the plausibility of such a deduction. The commandments are presented in the Hebrew order instead of the Catholic/Lutheran one.

First Commandment[edit]


A simple understanding of this commandment is that God (YHVH) is bigger and better than all the other gods, so to worship the others is to misattribute God's works. A more profound understanding would be to acknowledge that every person has some value that is paramount to them (career, money, power, ego etc.) Thus it can be said that everybody 'worships' something. Importantly, what we value most influences every aspect of our life. This commandment takes precedence to highlight that the only person you should give highest worth to is God.

Nevertheless, this commandment can only be connected to natural law for Theists who believe that God created humanity and that He is necessary for humanity to live -- making it not an integral part of natural law.

Second Commandment[edit]


In the Israel of those days, idol worship was associated with such things as child sacrifice, prostitution, and general debauchery. Also, when the Jews would commence idol worship it tended to diminish their status as distinct from the other nations around them, so objections could be raised to idol worship among Jews in the same way that objections are raised to American Indians abandoning their folk customs in favor of Christianity.

So this made some sense for the Jews of that time, but not universally — especially now that about half of the world's population worships YHVH.[3]

Third Commandment[edit]


This might be inferred in the same manner as the ironic saying, "Don't pray for anything; your prayer might actually be answered." Even if person A in a fit of exasperation yelled at person B, "God damn you!", A would probably be most alarmed at the prospect that his request would actually be carried out and B placed in hell for eternity.

Fourth Commandment[edit]


This is partly a ceremonial commandment, but according to Thomas Aquinas there is a moral component as well: "Give some time to the things of God."[4]

It might be argued that if one does not do this, one's dedication to one's religion goes down the tubes as well; during the Industrial Revolution, church attendance plummeted in a number of countries, and the level of religious adherence along with it. Aquinas' Catholic Church loudly protested at factory owners not giving workers time off to attend mass because of this.

Then comes the problem of the clergy: do religious services they perform count as work for them, especially since they necessarily perform these services on the Sabbath?

Fifth Commandment[edit]


In the old days, great strife was caused by family feuds — on a national level if they occurred in royal houses so that all of the population often had to take one side or the other. Also, in those days, being kicked out of your community as a result of a dispute with your parents often meant a life of destitution.

Even today, departing from one's family on bad terms is often followed by much struggle, hardship, existential crisis, psychotherapy, etc., etc. Although the tendency is to blame this on the family rather than the departure, it is undeniable that feeling alienated in the world can do terrible things to a person's mental health, and that being alienated can do terrible things to a person's temporal well-being. This is (explicitly or implicitly) understood by sects that practice shunning of unbelievers, such as the Amish or Scientology, since they use it partly as a way to punish those who stray from the faith.

Sixth Commandment[edit]

Thou shalt not kill.

Murder is one of those things that Thomas Aquinas categorizes as "things which the natural reason of every man, of its own accord and at once, judges ... not to be done."[5] It seems a universal thing to say that a person should not be killed unless he has it coming to him, the disagreements being only about who has what coming, and that is classed as a matter for humans to decide.[6]

Seventh Commandment[edit]

Thou shalt not commit adultery.

Although the merits of committing adultery were much promoted in the 1960s, it soon became apparent that adultery is not all it is cracked up to be; here are a few reasons why.

Owing to people's natural jealousy, adultery is responsible for the breaking up of certain families that might not otherwise have been broken up, causing strife and misery for all involved. Also, if one has struck a prior agreement (as in marriage vows) not to commit adultery, very few people would attempt a sound justification of acts breaking this agreement.

Before the invention of modern birth control, such infidelities tended to produce evidences in volume. If (as was the case) these children were stigmatized for being born out of wedlock, both they and their mothers could be put through hell. If on the other hand they were not stigmatized, it tended to throw fathers into a tricky situation, in which they could not spend as much time with their children as they might have otherwise; and although it is disputed exactly how much children need both parents involved in their upbringing, it is less disputed that problems arise when parents are not with their children for a proportion of time satisfactory to both parties.

Adultery was in the past the main conduit for STDs to spread in the population; combined with infidelity in non-marital committed relationships, it still comprises a large proportion of said conduit.[citation needed] A prominent example was the AIDS epidemic disproportionately hitting the gay community,[citation needed] when that community was engaging in much casual sex following the removal of long-standing restraints and legal harassment. This function of adultery has only partially been addressed now with the "safe sex" initiatives. It is not unthinkable that the Seventh Commandment was instituted at least partially for this reason; other parts of the Mosaic Law used the idea of ceremonial uncleanliness to quarantine lepers.[7]

Eighth Commandment[edit]

Thou shalt not steal.

This one has landed in the middle of modern-day political disputes, with right-wingers citing it to defend capitalism, and left-wingers citing it in opposition to capitalism on the grounds that the modern-day capitalist economies were built with stolen property.

On the other hand, Thomas Aquinas states that the application of this commandment is in the remit of humanity.[6] It seems to be universally agreed upon that if property is to be seized, it must be by due process of law; even those who adhere to the doctrine that "property is theft" tend to start protesting when regimes reach the stage where due process is not given.

Ninth Commandment[edit]

Thou shalt not bear false witness against thy neighbour.

Perjury is another one of those things that people rarely attempt to justify.

Tenth Commandment[edit]


Firstly, to clear up a misconception: Covetousness does not equal desire alone. To covet, one must (1) desire the thing in question, and (2) actively hatch a plot to get it away from the neighbor.[citation needed]Luther's Small Catechism expounds on this commandment (two commandments according to the Catholic/Lutheran division) as follows:

We should fear and love God that we may not craftily seek to get our neighbor's inheritance or house, and obtain it by a show of [justice and] right, etc., but help and be of service to him in keeping it. We should fear and love God that we may not estrange, force, or entice away our neighbor's wife, servants, or cattle, but urge them to stay.[8]

This is another commandment that has come up in modern political debates, with left-wingers accusing corporate big-shots of coveting everyone else's property and right-wingers accusing left-wingers of coveting the corporate big-shots' property.[9]

However, the "applicability" point comes up here again, as it is not agreed between right-wingers and left-wingers who actually owns the property in question, or if it is even property at all. On the other hand, there are very few people who, allowing that person A owns some property, will attempt to justify the actions of person B in coming by it dishonestly, or plotting the same.

As evidence of this, in the works of Ayn Rand, grandmother of all greed-boosters, it was the villains who were portrayed as covetous -- the "looters" who took property by force, the "moochers" who claimed it by tears, and the corrupt businessmen who had grown to prominence by acquiring other people's businesses through government connections and swallowing them up into vast amalgamations. The heroes, on the other hand, were people who built up their own businesses and created wealth without attempting to get their hands on anyone else's.


Although several of the Ten Commandments are at least partially deducible from natural law, or common sense, others are not. This would tend to put the lie to the argument from morality, which would only work if the entire law were revealed in nature (as a "watermark" of sorts).


  1. Summa Theologica, Prima Secundae, Q100 A1 [1]
  2. Summa Theologica, Prima Secundiae, Q100 A3 [2]
  4. Summa Theologica, Prima Secundae, Q100 A3 RO3 [3]
  5. Summa Theologica, Prima Secundae, Q100 A1 Body P2 [4]
  6. 6.0 6.1 Summa Theologica, Prima Secundae, Q100 A8 RO3 [5]
  7. Leviticus 13.
  9. To complete this circle, the corporate big-shots would have to accuse the right-wingers of something, and indeed they do: many such big-shots do not appreciate right-wingers legislating morals, which tends to be bad for business.