We will call them Naturalism and Legalism. Naturalism says we should just accept and live by our instincts. That seems to offer a way to live freely and without guilt. But we already know that our instincts will never choose to turn the other cheek, go the extra mile, pray for others, love neighbours and even enemies. That is why Naturalism is no solution for those who want to take up their cross as Christians.
Legalism is much more plausible.
It is the attempt to perfect oneself by human effort. And that is done by forcing our flesh into submission to the law. Admittedly we know strong minded people who manage to beat down and control some of their instincts. But we do not find such people particularly attractive. They easily become self-righteous and condemning.