Before the fall of Adam sinless man was able to sin. For God said, “In the day that you eat of it you shall surely die” (Genesis 2:17).

As soon as Adam fell, sinful man was not able not to sin, since we were unbelieving,and “whatever is not from faith is sin” (Romans 14:23).

When we are born again, by the power of the Holy Spirit we are able to not sin, for “sin will have no dominion over you” (Romans 6:14).

This means that what Paul calls “the natural man” or “the mind of the flesh” is not able not to sin. Paul says this in Romans 8:7-9

The mind that is set on the flesh is hostile to God, for it does not submit to God’s law; indeed, it cannot. Those who are in the flesh cannot please God. (See also 1Corinthians 2:14).

How then shall we think of free will?

It is not a saving power. In his freedom to will, fallen man cannot on his own do anything but sin. Such “free will” is a devastating reality. Without some power to overcome it’s bent, our free will only damns us.

We could stop here and turn with joy to the gospel truth that God overcomes our resistance, gives us life, wakens our dead inclination for Christ, and freely and irresistibly draws us to himself (John 6:44, 65; Acts 13:48; Ephesians 2:5; 2 Timothy 2:25-26).

Thanks to John Piper