It can be years before we realise the truth about something from which we need to repent and change our behaviour. We will have opinions when we discover the living Christ and receive the truth of His coming into the world. It might be years of following the teachings of Christ before we even realise what it means that He is the Christ. So we will start with such beliefs and a few opinions about right and wrong. We don't have to start with complete knowledge of right and wrong as God sees it. We have to start with belief in how special Jesus Christ is and how God sent Him for us. Then we need to learn truth according to the promise of it that following Jesus includes. We need certainty from Christ by the Spirit to be set free of sin, not mere strong opinions from others where others will have opinions conflicting with eachother. We need righteousness to be as promised us in Christ where we repent in confidence.
