Natural law is the reflection of God’s moral character and the moral order of creation, as designed by God, which is written on the human heart and evident through the light of nature (Rom. 2:14-15; Rom. 1:19; 1 Cor. 5:1), but held in unrighteousness (Rom. 1:18; Jer. 17:9; Prov. 14:12), whose substance is no different than the ten commandments. It is “the practical rule of moral duties to which men are bound by nature” (Turretin, Institutes, XI.i.5).
“For when the Gentiles, which have not the law, do by nature the things contained in the law, these, having not the law, are a law unto themselves: Which shew the work of the law written in their hearts, their conscience also bearing witness, and their thoughts the mean while accusing or else excusing one another” (Rom. 2:14-15).
The ten commandments are a summary of the moral law (Deut. 10:4; Ex. 34:1-4; Matt. 22:37-40). Every moral law fits into one of those ten categories. “Love is the fulfilling of the law” (Rom. 13:10), which is why the first four commandments are explained by Deut. 6:5, “And thou shalt love the Lord thy God with all thine heart, and with all thy soul, and with all thy might,” and the last six commandments are explained by Lev. 19:18, “thou shalt love thy neighbour as thyself.“
It is not called “natural” because it originates from nature apart from God, but because it is revealed by God through nature; and that in two ways, it is innately known in the conscience and it is acquired by sound reason about the created order. Natural law is best understood in two categories, 1) The reflection of God’s moral character, which cannot be otherwise, and 2) The moral order of creation as designed by God, which could have been otherwise. Francis Turretin wonderfully explains this distinction:
“The moral law as to all its precepts is simply indispensable because it contains the intrinsic reason of justice and duty; not as proceeding from the law, but as founded on the nature of God and arising from the intrinsic constitution of the thing and the proportion between the object and act, compared with right reason or the rational nature… all the precepts are not equally based on the primary right of nature, but some flow absolutely from the nature of God and command such things as God wills most freely indeed but yet necessarily (and so necessarily and immutably that he cannot will the contrary without a contradiction). However, other precepts depend upon the constitution of the nature of things (the free will of God coming in between) so they should not be thought to hold an equal degree of necessity and immutability. Although a dispensation properly so called does not have place in them, still a declaration or interpretation is sometimes given concerning them, the circumstances of the things or persons being changed.”
Institutes of Elenctic Theology, XI.ii.10-11.
Let us look at some examples of each and then finish with a discussion about how divine positive law is superadded to natural law.
1) The reflection of God’s moral character, which cannot be otherwise.
The primary laws of nature, being rooted in God’s moral character, cannot be anything but what they are. Here are a few examples:
“God is not a man, that he should lie” (Num. 23:19), therefore lying is sinful. Irreverent, vain, or misuse of God’s name is sinful because he is “the Lord thy God,” and he “will not hold him guiltless that taketh his name in vain” (Ex. 20:7), not because of some way that he chose to create the world. It is sinful to attempt to visually depict God because God is Spirit and cannot be seen, it is an ontological impossibility. “To whom then will ye liken God? or what likeness will ye compare unto him?” (Isa. 40:18). “Forasmuch then as we are the offspring of God, we ought not to think that the Godhead is like unto gold, or silver, or stone, graven by art and man’s device” (Acts 17:29). God has no parts and does not reveal Himself in parts because that is contrary to His nature and therefore impossible. It is sinful to have other gods before him because “the Lord is the true God, he is the living God, and an everlasting king” (Jer. 10:10). More examples could be given, but this will suffice.
All of these moral principles are grounded in the character of God, and cannot be otherwise because God does not change, they are necessarily moral. Unlike the secondary laws of nature, they do not derive their moral quality from God’s free decrees of creation and providence.
2) The moral order of creation as designed by God, which could have been otherwise.
The secondary laws of nature are drawn from the moral order of creation as designed by God rather than directly from God’s moral character. This does not make them any less morally binding, however, because they are still part of God’s moral will for mankind. While the precepts of the primary laws of nature cannot be otherwise, the secondary laws of nature theoretically could have been otherwise if God had chosen to create differently (cf. Turretin, Institutes, XI.ii.6).
Gender and procreation are elements of natural law, but are created. They could have been otherwise, but the way they were created establishes ethical norms for their use. For example, men having short hair and women having long hair (1 Cor. 11:14-15; note that Num. 6:5 describes a temporary divine positive law, a superadded sign of being set apart for a specific purpose in the old covenant); women wearing head coverings to corporate worship (1 Cor 11:4-12); clothing (Gen. 3:7, 21); “vile affections” (Rom. 1:26; cf. 2 Tim. 3:3) for “strange flesh” (Jude 7) and acts that are against “the natural use of the woman” (Rom. 1:27); etc.
The law of nature teaches that “a due proportion of time be set apart for the worship of God” (WCF 24:7), but without divine positive law it cannot be determined which day of the week should be set apart. Peter Martyr explained that “God could indeed have appointed all or many days for His own worship; but since He knew that we were doomed to eat our bread by the sweat of our face, He rested one in seven, on which, discarding other works, we should apply to that alone.” And Bullinger, on Matthew 12, states, “Sabbath signifies rest, and is taken for that day which was consecrated to rest. But the observance of that rest was always famous and of highest antiquity, not invented and brought forth for the first time by Moses when he introduced the law; for in the Decalogue it is said, ‘Remember the Sabbath-day to keep it holy,’ thereby admonishing them that it was of ancient institution.”
Philip Melanchthon illustrates this natural aspect of the 4th commandment as well as the positive aspect regarding God’s particular appointment of the 7th day in the old covenant (and his particular appointment of the 1st day in the New Covenant) [Turretin makes the same distinction in Institutes XI.ii.3]:
“In this commandment there are properly said to be two parts—the one natural, the other moral [positive]; the one the genus, the other the species. Of the former it is said, that the natural part or genus is perpetual, and cannot be abrogated, as being a command concerning the maintenance of the public ministry, so that on some one day the people should be taught, and divinely appointed ceremonies handled. But the species, which bears respect to the seventh day in particular, is abrogated.”
Notice how Westminster Confession 24:7 articulates this natural/positive distinction in the 4th commandment:
“As it is of the law of nature that, in general, a due proportion of time be set apart for the worship of God; so, in his Word, by a positive, moral, and perpetual commandment, binding all men in all ages, he hath particularly appointed one day in seven for a Sabbath, to be kept holy unto him (Exod 20:8, 10-11; Isa 56:2, 4, 6-7): which, from the beginning of the world to the resurrection of Christ, was the last day of the week; and, from the resurrection of Christ, was changed into the first day of the week (Gen 2:2-3; Acts 20:7; 1 Cor 16:1-2), which in Scripture is called the Lord’s day (Rev. 1:10), and is to be continued to the end of the world, as the Christian Sabbath (Exod 20:8, 10 with Mat 5:17-18).”
The circumstantial and positive appointment of the 7th day as the Sabbath no more abrogates the 4th commandment than the circumstantial and positive promise “that thy days may be long upon the land which the Lord thy God giveth thee” abrogates the 5th commandment to “honour thy father and thy mother” (Ex. 20:12). The land promise is circumstantial (yet applicable in the New Covenant in terms of longevity, Eph. 6:2-3) while the command for inferiors to honor their superiors (and the responsibilities of superiors to their inferiors) is rooted in the moral order of creation (cf. WLC Q. 123-133).
Divine Positive Law is Superadded to Natural Law
In addition to natural law, God has seen fit to make other laws that are not discernible by the light of nature and which require supernatural revelation. While natural law was “just and good antecedently to the command of God” (Turretin, Institutes, XI.i.4), divine positive law is just and good because of the command of God. All law cannot be positive law or else God would be free to command hatred of himself, which would be absurd. Divine positive law is not any less binding because it is just as much part of God’s moral will for whom it is given. John Owen compares divine positive law with the two categories of natural law explained above.
“There are two sorts of laws whereby God requires the obedience of his rational creatures, which are commonly called moral and positive…
Positive laws are taken to be such as have no reason for them in themselves – nothing of the matter of them is taken from the things themselves commanded – but do depend merely and solely on the sovereign will and pleasure of God. Such were the laws and institutions of the sacrifices of old; and such are those which concern the sacraments and other things of the like nature under the New Testament.
Moral laws are such as have the reasons of them taken from the nature of the things themselves required in them; for they are good from their respect to the nature of God himself, and from that nature and order of all things which he hath placed in creation. So that this sort of laws is but declarative of the absolute goodness of what they do require; the other is constitutive of it, as unto some certain ends.
Laws positive, as they are occasionally given, so they are esteemed alterable at pleasure. Being fixed by mere will and prerogative, without respect to any thing that should make them necessary antecedent to their giving, they may by the same authority at any time be taken away and abolished.”
Exercitations Concerning the Day of Sacred Rest, Excer. 4, pgs. 75-76. (cf. Turretin, Institutes, XI.i.4).
This distinction between natural and positive is implicit in Scripture, such as:
“And Samuel said, Hath the Lord as great delight in burnt offerings and sacrifices, as in obeying the voice of the Lord? Behold, to obey is better than sacrifice, and to hearken than the fat of rams” (1 Sam. 15:22).
“For I desired mercy, and not sacrifice; and the knowledge of God more than burnt offerings” (Hos. 6:6; cf. Jer. 7:21-23).
“Circumcision is nothing, and uncircumcision is nothing, but the keeping of the commandments of God” (1 Corinthians 7:19).
“Woe unto you, scribes and Pharisees, hypocrites! for ye pay tithe of mint and anise and cummin, and have omitted the weightier matters of the law, judgment, mercy, and faith: these ought ye to have done, and not to leave the other undone” (Matt. 23:23).
What makes some matters of the law “weightier” than others is that they are eternal and unchanging since they flow from the character of God or his moral order of creation. Whereas the ceremonial and judicial laws of Israel were “imposed on them until the time of reformation” (Heb. 9:10), “till the seed should come to whom the promise was made” (Gal. 3:19).
Divine positive law is the only way God’s people know how to worship him correctly. God is not “worshipped with men’s hands” (Acts 17:25), all forms of worship devised by man are detestable to him, this is the basis of the second commandment and the Regulative Principle of Worship. It can be known from nature that we must worship God how he pleases rather than how we please (Acts 17:24-29), but we cannot know how God desires to be worshiped unless he reveals it to us via positive law. “Thou art good, and doest good; teach me thy statutes” (Psalm 119:68). (cf. The Second Commandment and the Light of Nature)
The way God regulated his worship in the old covenant temple cultus (dietary laws, sacrifices, priests, ceremonial holy days, etc.) is different than how he regulates it now in the New Covenant, but the principle remains that “the acceptable way of worshipping the true God is instituted by himself, and so limited to his own revealed will, that he may not be worshipped according to the imaginations and devices of men, or the suggestions of Satan, under any visible representations or any other way not prescribed in the Holy Scripture ( Exod 20:4-6; Deut 4:15-20; 12:32; Mat 4:9-10; 15:9; Acts 17:25; Col 2:23).” While the purpose for which God commanded the old covenant ceremonial law is fulfilled and no longer binding (Dan. 9:27; Eph. 2:15-16; Col. 2:14-17), natural law and the positive commandments of the New Covenant (such as baptism, the Lord’s Supper, the Lord’s Day, etc.) remain binding for us today.