Strictly speaking good theology is what the Bible says about God and his will and his character. It was Jesus who said that the truth will set us free. Today our world follows what has been called the false trinity of tolerance, diversity, and pluralism. It is only the truth of God that sets men free. It is good biblical theology that speaks of God as holy and we human creatures as sinful. Good theology says that God has a plan to redeem men from their state of sin and that plan centers on the person of Christ and his redemptive death on the cross. Bad theology leads us to believe we are ok and that the cross is overrated.
After we come to Christ, Jude tells us in his letter in v. 20 that we are to build ourselves up in our most holy faith. Our faith is "holy" because it comes from a holy God. We do not have the right to change the Christian faith just because we find it uncomfortable or unpopular. To redress and modify God's truth will lead us into all kinds of harmful and dangerous practices. In fact it can be eternally devastating. God's truth protects us because it leads us to His perfect will for His creatures. Good theology says God is good and faithful. What is happening to me is not some slip in the cosmic fabric of the universe but the caring hands of my God molding my life for the greatest blessing of all. God has a purpose and God loves sinners in spite of their sin. That truth leads me to drop my defenses and embrace by faith God's invitation to be rescued. So many things do not last here, yet good theology says "God's mercies endure forever." That is what the Bible teaches and that's good theology. And it does save our lives! We need not live in despair, in doubt, in hopeless anguish, and in fear that nothing in this world is real. Believe the truth. Count on it. Good theology will save your life. Think it through.