Especially notable today considering our excessively self-indulgent, materialistic, and lusful society.
From: Romans 1:16-25
The Theme of the Epistle
 For I am not ashamed of the gospel: it is the power of God for salvation to every one who has faith, to the Jew first and also to the Greek. For in it the righteousness of God is revealed through faith for faith; as it is written, "He who through faith is righteous shall live."
The Fault and Punishment of the Gentiles
 For the wrath of God is revealed from heaven against all ungodliness and wickedness of men who by their wickedness suppress the truth.  For what can be known about God is plain to them, because God has shown it to them.  Ever since the creation of the world his invisible nature, namely, his eternal power and deity, has been clearly perceived in the things that have been made. So they are without excuse;  for although they knew God they did not honor him as God or give thanks to him, but they became futile in their thinking and their senseless minds were darkened.  Claiming to be wise, they became fools,  and exchanged the glory of the immortal God for images resembling mortal man or birds or animals or reptiles.
 Therefore God gave them up in the lusts of their hearts to impurity, to the dishonoring of their bodies among themselves,  because they exchanged the truth about God for a lie and worshipped and served the creature rather than the Creator, who is blessed for ever! Amen.
16. St Paul continues to speak about the "Gospel". The proclamation of the saving power of Christ's death on the Cross is a stumbling block to the Jews and foolishness to the Gentiles, whereas a Christian is proud of the Cross and draws strength from it. When writing to the Romans, the Apostle, who was quite familiar with the noise of triumphal marches and the divinization of emperors, simply says that "he is not ashamed; he does so to encourage them also not to be ashamed but, rather, to boast as he did. If today someone approaches you and asks you, 'But...do you adore a crucified man?', far from hanging your head and blushing with confusion, use this reproach as an opportunity to boast and let your eyes and your face show that you are not ashamed. If they come back and ask you aloud, 'What, adore the crucified?', reply: 'Yes, I adore him [...]. I adore and boast of a crucified God who, by his Cross, reduced the demons to silence and did away with all superstition: for me his Cross is the ineffable trophy of his benevolence and of his love"' (St John Chrysostom, "Hom. on Rom", 2).
17. The _expression "righteousness of God" refers to the state of righteousness or justice (= justness) in which a person is placed when God gives him grace. It is called the righteousness of God because man cannot attain it through his own efforts: it is a free (gratuitous, hence "grace") gift of God. The fact that "righteousness" comes from God does not mean that it is something external to man, for righteousness does not mean merely that we are called "righteous" but that we really are righteous in God's eyes. The Magisterium of the Church has given solemn teaching on this matter in the context of explaining the various factors which cause man's justification; "Finally", says the Council of Trent, "the only formal cause is 'justice of God, not the justice by which he is himself just, but the justice by which he makes us just' (St Augustine, "De Trinitate", XIV, 12, 15), namely, the justice which we have as a gift from him and by which we are renewed in the spirit of our mind. And not only are we considered just, but we are truly said to be just, and we are just" ("De Iustificatione", chap. 7).
"Through faith for faith": Sacred Scripture tends to use this kind of phrase to indicate on-going growth in something that is living (cf. Ps 84:8; 2 Cor 2:16; 3:18; Rom 6:19). What is being spoken about here is a steady progression from the imperfect understanding of divine truths possible in this life to the perfect understanding that is experienced in heaven. The full meaning of the phrase can be seen from St Paul's statement that in the Gospel justice is made manifest: it begins and is nourished and grows through faith, until the believer at last attains eternal salvation.
The statement that "he who through faith is righteous shall live" comes from Hab 2:4; St Paul here applies it to the position of the Christian. What the prophet meant was that those Jews who kept the Law and trusted in its promises would not succumb when the Babylonians invaded. St Paul applies the test to the righteous of the New Testament: if they stay firm in their faith in the Gospel, they will continue in the life of grace and will attain everlasting beatitude. The faith of good Israelites was a prefiguring of the faith of good Christians. The just man will live by faith, which "faith is the beginning of man's salvation, the foundation and source of all justification, 'without which it is impossible to please God' (cf. Heb 11:6) and to be counted as his sons" (Council of Trent, "De Iustificatione", chap. 8).
St Paul's statement can also be understood as meaning that he who through faith is just will live. This puts the emphasis on the fact that faith is the beginning of the process of justification, and that a person who is justified will attain salvation.
18-32. The Apostle is saying that the righteousness of God (= justness) can only come about through faith in Jesus Christ--and that neither Jews nor Gentiles possess this righteousness. He develops this point up as far as 3:20.
In the present passage he describes two stages in the position of the Gentiles. In the first (vv. 18-23) he points out their blameworthiness, and then in the second he goes on (vv. 24-32) to speak about the punishment of their sins. Justice as the righteousness of God refers to God's action of saving sinful man by pouring his grace into him; God's "wrath" is the punishment which the Almighty inflicts on him who persists in sin. For, as St Thomas says, "Anger and the like are ascribed to God by an analogy drawn from their effects. Because it is characteristic of anger that it stimulates men to requite wrong, divine retribution is analogically termed anger" ("Summa Theologiae", I, q. 3, a. 2 ad 2).
There is a connection between faith and righteousness, on the one hand, and sin and God's wrath, on the other. This Pauline teaching ties in with the last thing St John the Baptist is recorded as saying in bearing witness to Christ: "He who believes in the Son has eternal life; he who does not obey the Son shall not see life, but the wrath of God rests upon him" (Jn 3:36).
Christian teaching often points out how God's desire that all sinners be saved (the "righteousness of God" as instrument of salvation) combines with his punishment of sin (the "wrath of God"). How perfect justice interfaces with perfect mercy is ultimately a mystery.
18. "Who by their wickedness suppress the truth": commenting on these words St Thomas writes: "Genuine knowledge of God has the effect of inclining a person to goodness. However, this knowledge of God can be frustrated, as if enchained, by a person's attachment to vice" ("Commentary on Rom, ad loc.").
Clearly St Paul is speaking here of those Gentiles who do know about God but who fail to appreciate their good fortune; their knowledge of God does not produce the result which should naturally flow from it--an upright life. We can see from what Paul says that man is naturally religious. He has a knowledge of God which is not just theoretical: it has implications for his whole life because it implies that he is intimately united to God. When a person does not follow the impulse of his very nature he is guilty of unrighteousness, for he should render God homage for being his Creator.
"All men, because they are persons, that is, beings endowed with reason and free will and therefore bearing personal responsibility, are both impelled by their nature and bound by a moral obligation to seek the truth, especially religious truth. They are also bound to adhere to the truth once they come to know it and direct their whole lives in accordance with the demands of truth" (Vatican II, "Dignitatis Humanae", 2).
Our dependence on God does not mean that we are less than free; on the contrary, it is rejection of all religious duties that leads to the shameful slaveries which Paul now goes on to list, for "religion is the greatest rebellion of a person who does not want to live like an animal, who is not satisfied and will not rest until he reaches and comes to know his Creator" ([St] J. Escriva, "Conversations", 73).
19-20. It is possible to know about God without his having to reveal himself in a supernatural way; we know this from the book of Wisdom (Wis 13:1-9), which says that pagans, who, led astray by the beauty and power and greatness of created things, took these things for gods, should have known that all this perfection etc. came from their Author, for "from the greatness and beauty of created things comes a corresponding perception of their Creator" (Wis 13:5).
This knowledge of God, which we term "natural", is not something easy to attain; but it can be attained and it is the best form of preparation for accepting supernaturally revealed truths, and for disposing us to honor and worship our Creator. Moreover, Revelation confirms the certainty which natural knowledge gives: "The heavens are telling the glory of God", the Psalmist exclaims, band the firmament proclaims his handiwork" (Ps 19:2). St Augustine reminds us that traces of the Creator are to be found in man, and, as we all know from experience, we have been made to know and love God and therefore our heart is restless until it rests in him (cf. "Confessions", I, 1, 1).
To sum up, we can say with St Thomas Aquinas that, in the natural order, man has two ways of discovering the existence of God--one, through reason that inner light by means of which a person acquires knowledge; the other, through certain external pointers to the wisdom of God, that is, created things perceivable through the senses: these things are like a book on which are imprinted traces of God (cf. "Commentary on Rom", 1:6).
Whichever of these routes is taken, "God, the origin and end of all things, can be known with certainty by the natural light of human reason from the things that he created" (Vatican I, "Dei Filius", chap. 2).
Recalling the core of Christian teaching about the nature of man, the Second Vatican Council states that "sacred Scripture teaches that man was created 'in the image of God' as able to know and love his Creator", and that "the dignity of man rests above all on the fact that he is called to communion with God. The invitation to converse with God is addressed to man as soon as he comes into being. For if man exists it is because God has created him through love, and through love continues to hold him in existence" ("Gaudium Et Spes", 12 and 19). The human mind, therefore, even when relying on its own resources can grasp various truths concerning God--first of all, his existence, and secondly, certain of his attributes, which St Paul sums up here as his "invisible nature", "eternal power" and "deity". By reflecting on the created world, we can learn about some of God's perfections; but, St Thomas Aquinas comments, only in heaven will we be able to see that these various perfections are all one with the divine essence. This is why St Paul talks about God's "invisible nature". Contemplation of the works of creation leads us to posit the presence of an ever-existing Creator, and brings us to discover his "eternal power". Finally, the word "deity" implies that God is transcendent: he is the Cause, superior to all other causes, and in him everything finds its explanation and ultimate purpose.
The fact that it is possible to know God by the use of natural reason means that pagans who chose not to worship him were blameworthy. Their position is comparable to that of contemporary atheists and unbelievers who deny or doubt the existence of God despite the fact that as human beings they do know him in some way in the depths of their conscience. The culpability of pagans as of modern unbelievers ("they are without excuse") derives from the fact that they fail to accept that God is knowable through the use of human reason; they both commit the same fault--that of refusing to render worship to God.
Of course, to some degree the attitude of atheists can be explained by historical, environmental, personal and other factors. However, it should not be forgotten that these do not justify atheism. However, "those who willfully try to drive God from their heart and to avoid all questions about religion, not following the biddings of their conscience, are not free from blame" (Vatican II, "Gaudium Et Spes", 19).
21-23. The Gentiles knew God but they failed to give him his due--to worship him in a spirit of adoration and thanksgiving. As a result they fell into polytheism (belief in a multiplicity of gods) and idolatry, as St Paul vividly describes: they worshipped images depicting men and women (the Greeks gave their gods human form) or animals (as was the case in Egyptian and other eastern religions).
In our own time idolatry does not take that form, but there are practices which can properly be called idolatrous. Man is naturally religious and if he does not worship the true God he necessarily has to find other things to take God's place. Sometimes it is himself that man makes the object of worship: the Second Vatican Council points out that "with some people it is their exaggerated idea of man that causes their faith to languish; they are more prone, it would seem, to affirm man than to deny God [...]. Those who profess this kind of atheism maintain that freedom consists in this, that man is an end to himself and the sole maker, with supreme control, of his own history" ("Gaudium Et Spes", 19 and 20). It also happens that people, by becoming enslaved to them, make gods out of the good things created by God for man's benefit--money, power, sensuality.
24-32. The sin of idolatry leads to the kind of moral disorder described by St Paul: every time man knowingly and willingly tries to marginalize God, that religious aberration leads to moral disorder not only in the individual but also in society.
God punishes the sin of idolatry and impiety by withdrawing his graces: that is what the Apostle means when he says that he "gave them up to the lusts of their hearts" (v. 24), "gave them up to dishonorable passions" (v. 26). St John Chrysostom, explaining these words, says: "The Apostle shows here that ungodliness brings with it violation and forgetfulness of every law. When Paul says that God gives them up, this must be understood as meaning that God leaves them to their own devices. God abandons the evildoer but he does not impel him towards evil. When the general withdraws in the thick of the battle, he gives his soldiers up to the enemy, not in the sense of physically shackling them but because he deprives them of the help of his presence. God acts in the same way. Rebels against his law, men have turned their back on him; God, his goodness exhausted, abandons them [...]. What else could he do? Use force, compel them? Those means do not make men virtuous. The only thing he could do was let them be" ("Hom. on Rom", 3).
It may be that God counts on the experience of sin to move people to repentance. In any event, we should not read into this passage unconcern, much less injustice on God's part: he never abandons people unless they first abandon him (cf. Council of Trent, "De Iustificatione", chap. 11).
25. When describing the blasphemous behavior of Gentiles who worship created things rather than the Creator, St Paul cannot but utter an ejaculation, in a spirit of atonement. This should teach us to do the same whenever we witness offense being offered to God.
Source: "The Navarre Bible: Text and Commentaries". Biblical text taken from the Revised Standard Version and New Vulgate. Commentaries made by members of the Faculty of Theology of the University of Navarre, Spain. Published by Four Courts Press, Kill Lane, Blackrock, Co. Dublin, Ireland.