All of our sins can be categorized under Legalism or Licentiousness. In self-righteousness, we do things that we think will earn us right standing with God, or we abstain from things in hopes that God will count us righteous. This is the sin of legalism; depending upon moral law for our right standing with God.
Licentiousness is when we completely ignore God’s law in pursuit of earthly fleeting pleasures. In doing so, we live as if God’s commands are arbitrary. Or we explain away the importance of obedience by twisting the grace of God into a free pass to sin.
J.D. Greear in his introduction to Titus in The Gospel Transformation Study Bible helps us identify the root of legalism and licentiousness, then shows us how the gospel is the only true remedy:
Definitions of Licentiousness and Legalism
“Licentiousness is reckless, godless, rule-free living. Legalism is dutiful, strict, dry living. The first takes advantage of the grace of God, the latter seeks to earn it. Though very different in their expressions, Paul shows that licentiousness and legalism grow from the same root: hope in the flesh for personal fulfillment. The licentious person feeds on the lusts of the flesh; the legalist feeds on pride in his flesh. Both paths result in spiritual fatigue, strife, sin, and eventually, hatred of God.”
The Remedy for Licentiousness and Legalism: The Gospel
“Paul shows that the answer to both licentiousness and legalism is the gospel. The gospel alone gives the security, love, and joy that the human heart craves. The gospel frees us from captivity to the lusts of the flesh and the need to exalt ourselves above others, as the absolute approval of the only One whose opinion really matters has been given to us as a gift in Christ. He is all we need for everlasting joy.”
The New Way: Longing For God
“Furthermore, the gospel creates in us something human religion is utterly unable to create: a “longing” for God. The gospel “trains our hearts” to pursue righteousness and to be zealous for good works (2:11–12). The good news does this not through threat of punishment or promise of reward but by making us stand in awe of the God who gave himself for us. Regulating the flesh cannot curb sinful desire any more than you can tame a wild animal by chaining it. Only a profound experience with God’s grace transforms the heart. The gospel gives us the satisfaction in God that curbs our desire for sin and the security in God that no failures on our part can threaten (2:11–14; 3:3–7).”