He repeats the objection with slight variation, so that he can take it one stage further in verse 8. This objection is something of a last resort, and yet Paul, and yet he will not leave it till he has flushed out his opponents from every refuge.
The principle put forward in this objection is so destructive that ultimately it would overthrow God himself. Both evil and good would appear to be working towards a common goal. Now it is a profound truth revealed in Scripture that God will make both good and evil to serve his glory (Proverbs 16:4). This seems to make God a debtor to evil, but Scripture assures us that God is good (Psalm 25:8), and there is no evil in him (Psalm 5:4; John 8:46; James 1:13), and he hates evil (Psalm 5:5; 45:7), and tells his people to hate evil (Proverbs 8:13; Psalm 97:10), that he will keep heaven pure (Revelation 21:27), and he is holy, separated from all evil. Evil and good are utterly separated to God, and if by wisdom evil is made to serve God’s purpose, this is not because he loves evil. His commandment to man has shown what his true feelings towards evil.