Now I know, brothers and sisters, that you acted out of ignorance, just as your leaders did…Repent, therefore, and be converted, that your sins may be wiped away.”
I find it very interesting that Saint Peter both acknowledges the mitigating circumstances of the peoples’ guilt (ignorance, poor leadership and moral/spiritual formation) and still exhorts them to full repentance anyway. This gives us a little insight into the Church’s way of dealing with grave matter and mortal sin. The Church teaches us that all sins involving grave matter (serious offenses against the dignity of God, God’s Law, God’s Church, or the dignity or life of human persons) must be confessed, even if they do not meet all the criteria to become truly mortal sins (full knowledge and consent of the will). The grave matter itself requires repentance, even if it has not fully cut us off from God. The offense is still real, intended or not; the effects of sin may still destroy us, even if we did not fully know what we were doing at the time. Repentance is an act of our will—our choice—to turn back to God in response to the invitation of the Holy Spirit to rebuild the relationship. The nature of our love relationship with God ought to convince us to act with full repentance for every sin, especially for all grave sins. We must love God and the things of God more than we love sin.