Luke 15:17-18, what do we see in these two verses. It states that when he came to himself that is saw his depraved state, he said within himself, I will arise and go into my Father. Now this son realized his sinful state just like unbelievers realize theirs. He says I will that is of his own free will he arose and went to the Father. The father didn't put this in him it says he came to himself, humbling himself and confessing himself a sinner. Isn't that what mankind must do humble themselves before God and confess themselves sinners in need of salvation. Christ perfectly shows us how everyone comes to the Father once they come to realize their own sinful state. Then there's the other brother who doesn't recognize his sin and sees himself as safe. He would be who says I did all these things for you Lord and will be told depart I never knew you. Volition played into both of their decisions and the sin nature was active in both until the one came to himself.