Charles Ellicott Commentary Romans 1:31

"without understanding, covenant-breakers, without natural affection, unmerciful:" — Romans 1:31 (ASV)

Without understanding—i.e., without moral or spiritual understanding; incapable of discriminating between right and wrong, expedient and inexpedient. St. Paul prays that the Colossians may possess this faculty (Colossians 1:9).

Without natural affection.—The affection founded upon natural relationship—e.g., between parent and child, husband and wife, brother and sister. In illustration of this particular expression, we may remember that infanticide and divorce were very common at this period.