True, the nominal Catholic she'd said that to exhibited a certain disparity between his professed belief in God and his day-to-day life. Though he'd once attempted to impress me with his claim to be a "Bible scholar" (I really fought hard to keep a straight face), everybody could see that Scripture made absolutely no impact on his moral choices. I believe the discrepancy between his claim of faith and his behavior prompted my girlfriend to describe Christianity as a "lifestyle."
Her description troubled me at the time, and it troubles me even more now. For while genuine salvation definitely leads to a lifestyle that increasingly renounces sin, that lifestyle merely shows evidence of the Holy Spirit's regenerative work in a believer. Moreover, outward morality can be mimicked by all sorts of people who don't believe the Gospel. The Pharisees of Jesus day held to a high moral code, remember, but they rejected Jesus Christ.
In fact, trusting in our own morality, even if we derive that morality from the Bible, completely contradicts the essence of the Gospel. Those who defend their Christianity on the basis that they go to church, read their Bibles daily, remain sexually pure (physically) and drink only in moderation prove only that they trust in their good works rather than in Jesus' atoning work on the cross. Oh, they may say otherwise (they know their responsibility to say all the correct things), but deep down they believe their religious activity and avoidance of certain behaviors is what distinguishes them from non-Christians.
Of course I believe that born-again Christians will grow in holiness, developing a disdain for sin. In that respect, we indeed do have a lifestyle that makes us different from those around us. The epistle of 1 Peter (obviously too lengthy to quote here) shows the relationship between regeneration and exhibiting the values of our Heavenly Father. In other words, we live a holy lifestyle because the Holy Spirit causes us to resemble our Father.
Christianity, then, differs from any other belief system in that God gives us new birth as we admit our own moral bankruptcy and trust in Christ's atonement.
1And you were dead in the trespasses and sins 2 in which you once walked, following the course of this world, following the prince of the power of the air, the spirit that is now at work in the sons of disobedience— 3 among whom we all once lived in the passions of our flesh, carrying out the desires of the body and the mind, and were by nature children of wrath, like the rest of mankind. 4 But God, being rich in mercy, because of the great love with which he loved us, 5 even when we were dead in our trespasses, made us alive together with Christ—by grace you have been saved— 6 and raised us up with him and seated us with him in the heavenly places in Christ Jesus, 7 so that in the coming ages he might show the immeasurable riches of his grace in kindness toward us in Christ Jesus. 8 For by grace you have been saved through faith. And this is not your own doing; it is the gift of God, 9 not a result of works, so that no one may boast. ~~Ephesians 2:1-9 (ESV)We point to His grace rather than our lifestyle. He alone deserves the spotlight because He is the One Who gave us the new life that, in turn, changes our values and behavior in ways that reflect Him. True conversion never points to self-accomplishment, but instead rejoices in the transforming grace of Jesus Christ.