Without understanding, {n} covenantbreakers, without natural affection, implacable, unmerciful:

(n) Not caring if they keep their covenants and bargains.

People's New Testament

1:31 Without understanding. Senseless, foolish.

Wesley's Notes

1:31 Covenant - breakers - It is well known, the Romans, as a nation, from the very beginning of their commonwealth, never made any scruple of vacating altogether the most solemn engagement, if they did not like it, though made by their supreme magistrate, in the name of the whole people. They only gave up the general who had made it, and then supposed themselves to be at full liberty. Without natural affection - The custom of exposing their own new - born children to perish by cold, hunger, or wild beasts, which so generally prevailed in the heathen world, particularly among the Greeks and Romans, was an amazing instance of this; as is also that of killing their aged and helpless parents, now common among the American heathens.

King James Translators' Notes

without natural...: or unsociable

Matthew Henry's Concise Commentary

1:26-32 In the horrid depravity of the heathen, the truth of our Lord's words was shown: Light was come into the world, but men loved darkness rather than light, because their deeds were evil; for he that doeth evil hateth the light. The truth was not to their taste. And we all know how soon a man will contrive, against the strongest evidence, to reason himself out of the belief of what he dislikes. But a man cannot be brought to greater slavery than to be given up to his own lusts. As the Gentiles did not like to keep God in their knowledge, they committed crimes wholly against reason and their own welfare. The nature of man, whether pagan or Christian, is still the same; and the charges of the apostle apply more or less to the state and character of men at all times, till they are brought to full submission to the faith of Christ, and renewed by Divine power. There never yet was a man, who had not reason to lament his strong corruptions, and his secret dislike to the will of God. Therefore this chapter is a call to self-examination, the end of which should be, a deep conviction of sin, and of the necessity of deliverance from a state of condemnation.