Question 8. Are we then so corrupt that we are wholly incapable of doing any good, and inclined to all wickedness?
Answer: Indeed we are; (a) except we are regenerated by the Spirit of God. (b)
(a) Gen.8:21 The imagination of man’s heart is evil from his youth; John 3:6 That which is born of the flesh is flesh; and that which is born of the Spirit is spirit. Gen.6:5 And GOD saw that the wickedness of man was great in the earth, and that every imagination of the thoughts of his heart was only evil continually. Job 14:4 Who can bring a clean thing out of an unclean? not one. Job 15:14 What is man, that he should be clean? and he which is born of a woman, that he should be righteous? Job 15:16 How much more abominable and filthy is man, which drinketh iniquity like water? Job 15:35 They conceive mischief, and bring forth vanity, and their belly prepareth deceit. Isa.53:6 All we like sheep have gone astray; we have turned every one to his own way; and the LORD hath laid on him the iniquity of us all. (b) John 3:3 Jesus answered and said unto him, Verily, verily, I say unto thee, Except a man be born again, he cannot see the kingdom of God. John 3:5 Jesus answered, Verily, verily, I say unto thee, Except a man be born of water and of the Spirit, he cannot enter into the kingdom of God. 1 Cor.12:3 Wherefore I give you to understand, that no man speaking by the Spirit of God calleth Jesus accursed: and that no man can say that Jesus is the Lord, but by the Holy Ghost. 2 Cor.3:5 Not that we are sufficient of ourselves to think any thing as of ourselves; but our sufficiency is of God.
The framers of the Catechism saw with crystal clarity the fact that unaided by the grace of God, good is utterly and thoroughly impossible for us. Good outside of God doesn’t exist. Only a form of it, an apparition, a fraudulent and deceptive untrue manifestation. ‘There is none good but God alone’ is 100% true.