Many have read in various scriptures that we are sinners from birth and heard scriptural characters saying: “The good I wish to do I do not do, but the bad I do not wish to do is what I do. What a wretched person I am!” or “This is the way God has made me” …etc. Reading such things people feel that sin is an inherited tendency—something normal.
But an analytical mind would not agree because he finds an avalanche of proofs against this. We find variety of people acting/reacting differently in same situation: Some do more righteous acts, some do more sinful acts, and others mix them in varying degrees, one-time sinners changing into saints, one-time saints changing into sinners, some very poor people who refuse to steal, and some very wealthy people who steal in various ways… etc. This shows people choose to act the way they like which means they are not sinners from birth—resulting in all sorts of people from sinless to the sinful ones. Interestingly, even Bible makes many references to some sinless persons who lived in the ancient times (Genesis 5:24; Job 1:8; Psalm 18:23; Ezekiel 14:14; Luke 1:6 …etc.) and human capacity to perform righteousness. (Habakkuk 2:4; Hebrews 10:38)
Doing good to the self/others is virtue; doing harm to the self/others is sin, hence it is within the power of any human to do good which they have done many times in their lives which means they can repeat it any number of time if they want.
Everything apostle Paul wrote about sin was his view.