Who show the work of the law [1] written, etc.; that is, they prove that there is imprinted on their hearts a discrimination and judgment by which they distinguish between what is just and unjust, between what is honest and dishonest. He means not that it was so engraven on their will, that they sought and diligently pursued it, but that they were so mastered by the power of truth, that they could not disapprove of it. For why did they institute religious rites, except that they were convinced that God ought to be worshipped? Why were they ashamed of adultery and theft, except that they deemed them evils? Without reason then is the power of the will deduced from this passage, as though Paul had said, that the keeping of the law is within our power; for he speaks not of the power to fulfill the law, but of the knowledge of it. Nor is the word heart to be taken for the seat of the affections, but only for the understanding, as it is found in Deuteronomy 29:4, "The Lord hath not given thee a heart to understand;" and in Luke 24:25, "O foolish men, and slow in heart to believe." Nor can we conclude from this passage, that there is in men a full knowledge of the law, but that there are only some seeds of what is right implanted in their nature, evidenced by such acts as these -- All the Gentiles alike instituted religious rites, they made laws to punish adultery, and theft, and murder, they commended good faith in bargains and contracts. They have thus indeed proved, that God ought to be worshipped, that adultery, and theft, and murder are evils, that honesty is commendable. It is not to our purpose to inquire what sort of God they imagined him to be, or how many gods they devised; it is enough to know, that they thought that there is a God, and that honor and worship are due to him. It matters not whether they permitted the coveting of another man's wife, or of his possessions, or of any thing which was his, -- whether they connived at wrath and hatred; inasmuch as it was not right for them to covet what they knew to be evil when done. Their conscience at the same time attesting, etc. He could not have more forcibly urged them than by the testimony of their own conscience, which is equal to a thousand witnesses. By the consciousness of having done good, men sustain and comfort themselves; those who are conscious of having done evil, are inwardly harassed and tormented. Hence came these sayings of the heathens -- "A good conscience is the widest sphere; but a bad one is the cruelest executioner, and more fiercely torments the ungodly than any furies can do." There is then a certain knowledge of the law by nature, which says, "This is good and worthy of being desired; that ought to be abhorred." But observe how intelligently he defines conscience: he says, that reasons come to our minds, by which we defend what is rightly done, and that there are those which accuse and reprove us for our vices; [2] and he refers this process of accusation and defense to the day of the Lord; not that it will then first commence, for it is now continually carried on, but that it will then also be in operation; and he says this, that no one should disregard this process, as though it were vain and evanescent. And he has put, in the day, instead of, at the day, -- a similar instance to what we have already observed.

Footnotes

1 - By the work of the law, to ergon tou nomou, is to be understood what the law requires. The "work of God," in John 6:29, is of the same import, that is, the work which God requires or demands; and the same word is plural in the former verse, ta erga -- "the works of God." So here, in the former verse, it is ta tou nomou -- "the things of the law," where we may suppose ergato be understood. The common expression, "the works of the law," has the same meaning, that is, such works as the law prescribes and requires. -- Ed.

2 - Calvin seems to consider that the latter part of the verse is only a expansion or an exposition of the preceding clause respecting "conscience:" but it seems to contain a distinct idea. The testimony of conscience is one thing, which is instantaneous, without reflection: and the thoughts or the reasonings -- logismon, which alternately or mutually accuse or excuse, seem to refer to a process carried on by the mind, by which the innate voice of conscience is confirmed. This is the view taken by Stuart and Barnes, and to which Hodge is inclined. Another view of the latter clause is given by Doddridge, Macknight, Haldane, and Chalmers The last gives this paraphrase of the whole verse, -- "For they show that the matter of the law is written in their hearts -- both from their conscience testifying what is right and wrong in their own conduct, and from their reasonings in which they either accuse or vindicate one another." But to regard the two clauses as referring to conscience and the inward workings of the mind, appears more consistent with the context. The Gentiles are those spoken of: God gave them no outward law, but the law of nature which is inward. Hence in the following verse he speaks of God as judging "the secrets of men," as the inward law will be the rule of judgment to the Gentiles -- Ed.

Which show - Who thus evince or show.
The work of the law - The design, purpose, or object which is contemplated by the revealed Law; that is, to make known to man his duty, and to enforce the obligation to perform it. This does not mean, by any means, that they had all the knowledge which the Law would impart, for then there would have been no need of a revelation, but that, as far as it went, as far as they had a knowledge of right and wrong, they coincided with the revealed will of God. In other words, the will of God, whether made known by reason or revelation, will be the same so far as reason goes. The difference is that revelation goes further than reason; sheds light on new duties and doctrines; as the information given by the naked eye and the telescope is the same, except, that the telescope carries the sight forward, and reveals new worlds to the sight of man.
Written in their hearts - The revealed Law of God was written on tables of stone, and then recorded in the books of the Old Testament. This law the Gentiles did not possess, but, to a certain extent, the same requirements were written on their hearts. Though not revealed to them as to the Jews, yet they had obtained the knowledge of them by the tight of nature. The word "hearts" here denotes the mind itself, as it does also frequently in the Sacred Scriptures; not the heart, as the seat of the affections. It does not mean that they loved or even approved of the Law, but that they had knowledge of it; and that that knowledge was deeply engraved on their minds.
Their conscience - This word properly means the judgment of the mind respecting right and wrong; or the judgment which the mind passes on the morality or immorality of its own actions, when it instantly approves or condemns them. It has usually been termed the moral sense, and is a very important principle in a moral government. Its design is to answer the purposes of an ever attendant witness of a man's conduct; to compel him to pronounce on his own doings, and thus to excite him to virtuous deeds, to give comfort and peace when he does right, to deter from evil actions by making him, whether he will or no, his own executioner: see John 8:9; Acts 23:1; Acts 24:16; Romans 9:1; 1-Timothy 1:5. By nature every man thus approves or condemns his own acts; and there is not a profounder principle of the divine administration, than thus compelling every man to pronounce on the moral character of his own conduct. Conscience may be enlightened or unenlightened; and its use may be greatly perverted by false opinions. Its province is not to communicate any new truth, it is simply to express judgment, and to impart pleasure or inflict pain for a man's own good or evil conduct. The apostle's argument, does not require him to say that conscience revealed any truth, or any knowledge of duty, to the Gentiles, but that its actual exercise proved that they had a knowledge of the Law of God. Thus, it was a witness simply of that fact.
Bearing witness - To bear witness is to furnish testimony, or proof. And the exercise of the conscience here showed or proved that they had a knowledge of the Law. The expression does not mean that the exercise of their conscience bore witness of anything to them, but that its exercise may be alleged as a proof that they were not without some knowledge of the Law.
And their thoughts - The word "thoughts" (λογισμῶν logismōn) means properly reasonings, or opinions, sentiments, etc. Its meaning here may be expressed by the word "reflections." Their reflections on their own conduct would be attended with pain or pleasure. It differs from conscience, inasmuch as the decisions of conscience are instantaneous, and without any process of reasoning. This supposes subsequent reflection, and it means that such reflections would only deepen and confirm the decisions of conscience.
The mean while - Margin, "Between themselves." The rendering in the margin is more in accordance with the Greek. The expression sometimes means, in the mean time, or at the same time; and sometimes afterward, or subsequently. The Syriac and Latin Vulgate render this mutually. They seem to have understood this as affirming that the pagan among themselves, by their writings, accused or acquitted one another.
Accusing - If the actions were evil.
Excusing - That is, if their actions were good.
One another - The margin renders this expression in connection with the adverb, translated "in the mean while," "between themselves." This view is also taken by many commentators, and this is its probable meaning. If so, it denotes the fact that in their reflections, or their reasonings, or discussions, they accused each other of crime, or acquitted one another; they showed that they had a law; that they acted on the supposition that they had. To show this was the design of the apostle; and there was no further proof of it needed than what he here adduced.
(1) They had a conscience, pronouncing on their own acts; and,
(2) Their reasonings, based on the supposition of some such common and acknowledged standard of accusing or acquitting, supposed the same thing. If, therefore, they condemned or acquitted themselves; if in these reasonings and reflections, they proceeded on the principle that they had some rule of right and wrong, then the proposition of the apostle was made out that it was right for God to judge them, and to destroy them; Romans 2:8-12.

Which show the work of the law - In acting according to justice, mercy, temperance, and truth, they show that the great object of the law, which was to bring men from injustice, cruelty, intemperance, and falsity, is accomplished so far in them: their conscience also bearing witness - that faculty of the soul, where that Divine light dwells and works, shows them that they are right; and thus they have a comfortable testimony in their own souls of their own integrity: their thoughts, the mean while, accusing, or else excusing one another; or rather, their reasonings between one another accusing or answering for themselves. As if the apostle had said: - And this point, that they have a law and act according to it, is farther proved from their conduct in civil affairs; and from that correct sense which they have of natural justice in their debates, either in their courts of law, or in their treatises on morality. All these are ample proofs that God has not left them without light; and that, seeing they have such correct notions of right and wrong, they are accountable to God for their conduct in reference to these notions and principles. These seems to be the true meaning of this difficult clause. See below.

Which shew the work of the law (l) written in their hearts, their conscience also bearing witness, and [their] thoughts the mean while accusing or else excusing one another;)
(l) This knowledge is a natural knowledge.

Which show the work of the law written in their hearts,.... Though the Gentiles had not the law in form, written on tables, or in a book, yet they had "the work", the matter, the sum and substance of it in their minds; as appears by the practices of many of them, in their external conversation. The moral law, in its purity and perfection, was written on the heart of Adam in his first creation; was sadly obliterated by his sin and fall; upon several accounts, and to answer various purposes, a system of laws was written on tables of stone for the use of the Israelites; and in regeneration the law is reinscribed on the hearts of God's people; and even among the Gentiles, and in their hearts, there are some remains of the old law and light of nature, which as by their outward conduct appears, so by the inward motions of their minds,
their conscience also bearing witness; for, as the Jews say (r) , "the soul of a man witnesses in him"; for, or against him:
and their thoughts the meanwhile accusing or else excusing one another; and this the Heathens themselves acknowledge, when they (s) speak of
"tameion dikasthrion kai krithrion thv suneidhsewv, "the conclave, tribunal and judgment of conscience"; and which they call , "the most righteous judge": whose judgment reason receives, and gives its suffrage to, whether worthy of approbation or reproof; when it reads in the memory as if written on a table the things that are done, and then beholding the law as an exemplar, pronounces itself either worthy of honour or dishonour.''
(r) T. Bab. Chagigah, fol. 16. 1. & Taanith, fol. 11. 1. (s) Hierocles in Carmina Pythagor. p. 81, 206, 209, 213, 214.

their thoughts the meanwhile accusing or else excusing--that is, perhaps by turns doing both.

Who show - To themselves, to other men, and, in a sense, to God himself. The work of the law - The substance, though not the letter, of it. Written on their hearts - By the same hand which wrote the commandments on the tables of stone. Their conscience - There is none of all its faculties which the soul has less in its power than this. Bearing witness - In a trial there are the plaintiff, the defendant, and the witnesses. Conscience and sin itself are witnesses against the heathens. Their thoughts sometimes excuse, sometimes condemn, them. Among themselves - Alternately, like plaintiff and defendant. Accusing or even defending them - The very manner of speaking shows that they have far more room to accuse than to defend.