Paul turns to the revealed Word of God in Romans 3 and concludes that “all have sinned and fall short of the glory of God.” The religious person is no better than the pagan. Listen to the litany of truth about the sinfulness of man found in Romans 3:10-18, quoting from the Psalms, Isaiah and Ecclesiastes.
“There is no one righteous, not even one; there is no one who understands, no one who seeks God. All have turned away, they have together become worthless; there is no one who does good, not even one.” “Their throats are open graves; their tongues practice deceit.” “The poison of vipers is on their lips.” “Their mouths are full of cursing and bitterness.” “Their feet are swift to shed blood; ruin and misery mark their ways, and the way of peace they do not know.” “There is no fear of God before their eyes.” Paul could have marshaled more quotations such as Jeremiah 17:9, “The heart is deceitful above all things and beyond cure. Who can understand it?”
He could’ve presented examples of many in past centuries who rejected the truth and arrogantly went their own way down the broad road to destruction. But he felt the quotes listed in Romans 3 are sufficient to silence every mouth and hold everyone accountable to God. Romans 3:20 declares, “Therefore no one will be declared righteous in his sight by observing the law; rather, through the law we become conscious of sin.”
The advantage of having divine revelation is that it confirms what we already know by our own conscience – we are all sinners.