What is the meaning of Romans 1:18?

18 For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who hold the truth in unrighteousness; (Romans 1:18 KJV)

William Burkitt’s Commentary

Our apostle having asserted and laid down a general proposition, that the justification of a sinner is only to be expected by the righteousness of the Mediator in a way of faith; he now undertakes the proof and demonstration of it thus; distributes the whole world into Gentiles and Jews; the former seeking righteousness by the dim light of nature or the law written in their hearts and the latter by the works of the law, that is by their external conformity to what the law of Moses exacted and required of them.

Now his present business is to prove distinctly and fully that neither Gentiles nor Jews could ever find what they thus sought. He begins here with the Gentiles and shows that indeed they had inbred notions of a God imprinted in their minds by nature, and also had the book of the creature before their eyes, in which much, very much of God, might be seen: yet these common notices of God, and of good and evil, they did not obey and put in practice but rebelled against the light and dictates of their natural consciences: for which cause, the wrath of God was revealed from heaven against them.

Here observe, 1. A dreadful manifestation of divine wrath:  The wrath of God is revealed from heaven. The wrath of God; that is, the indignation or vengeance of God: This the sinner shall feel who does not fear it; for the fears of an incensed Deity are no bug-bears, nor the effects of ignorance and superstition as the Atheists fancy. This wrath is said to be revealed from heaven; that is, discovered and made manifest by the God of heaven, partly by the light of nature, their own consciences giving them notice and warning of it; and partly by the examples of others, in the lashes of a divine severity on the back of sinners, by the hand of an incensed God:  Thus the wrath of God was revealed to the Gentiles from heaven.

Observe, 2. The object or impulsive cause of his revealed and inflicted wrath; namely,  All ungodliness and unrighteousness of men. Ungodliness comprises all sins against God, or neglect of the duties of the first table: Unrighteousness comprehends all sins against our neighbour or the breaches of the second table.

Note here, That the abstract is put for the concrete, the sins for the sinners that commit them; the wrath of God is revealed against all ungodliness and unrighteousness of men; that is, against all ungodly and unrighteous persons; the meaning is, that God will certainly punish these sins upon the persons of the sinners.

Observe, 3. The special aggravation of these their sins, or that which made them so very provoking to Almighty God; namely, that they held the truth in unrighteousness; that is, their natural convictions were kept down under the dominion and power of their corruptions. Lust in their wills and affections was too hard for the light in their understandings; they entertained the light of truth in their minds, but did not allow it to have its proper effect and influence upon their hearts and lives; thus making that a prisoner which would have made them free.

Learn, 1. That it is a very great aggravation of sin, for men to offend against the light of their own minds, and to rebel against the convictions of their own consciences.

2. That the wrath of God is dreadfully incensed against all those that live in any course of sin, rebelling against the dictates and convictions of their own enlightened consciences.

Dread it then, as thou dreadest hell itself, to sin against knowledge, to rebel against the light of thy own mind, to slight the whispers, to stifle the voice of thy own conscience; but reverence and obey its dictates as the commands of God.