I heard a man I respect (religious, but not Christian) object to the Christian idea that a person can only get to heaven “through Christianity,” his response being that “God cares more about behavior than theology.” That is, the Christian idea (or rather, what he understands to be the Christian idea) that it’s belief in Jesus that makes a person heaven-worthy doesn’t make sense to him. God is clearly concerned about moral categories—good and evil. Therefore, he says, it doesn’t matter what you believe, as long as you’re a good person.
But this man has misunderstood Christianity. The difference between us is not that Christians think God doesn’t care about behavior, the difference is that Christians think God cares a great deal more about behavior than this man thinks God cares.
This man thinks his behavior passes God’s standard for heaven-worthy behavior, but Christians think the standard is much higher—that the standard is perfect, in fact, and that God’s holiness would rightly destroy any of us who tried to stand before Him based on our behavior. In other words, God cares so much about behavior that we all face His righteous and perfect condemnation.
Is this too high a standard? Does this make God unreasonable? No, this makes God perfectly just. This man wants God to care about moral categories. The bad news for Him is that He does. Perfectly and completely. There’s no grading on a curve, there’s no compromising justice.
This puts us in a very bad position. When Isaiah—a very prophet of God who wrote part of the Bible, no less—came face to face with God, He realized what a bad position he was in, crying out, “Woe is me, for I am ruined! Because I am a man of unclean lips, and I live among a people of unclean lips; For my eyes have seen the King, the Lord of hosts" (Isaiah 6:5).
From the murderer who considers himself a good person (as I read in a blog post by a murderer in prison once) to this man who wants God to care about behavior, we all fool ourselves into thinking we’re good by comparing ourselves to the sinful people around us. We can all pass the test if we just lower the standard. But as with Isaiah, when we finally see Perfection, we will see ourselves as we really are and despair.
So Christianity takes behavior quite seriously. Nothing in Christianity would make sense without that. The reason Christians think we need to trust in Jesus and be joined to Him in order to be heaven-worthy is that we need Him to stand before God in our place precisely because His behavior was perfect and His sacrifice on the cross fulfilled the justice we deserved on our behalf. In this way only can we stand—not because God will lower His standard for us, but because He upheld His perfect righteousness and justice through Jesus.
The alternative is to say that God doesn’t perfectly care about behavior or justice—that He’s willing to accept a certain level of sin. That is not a good alternative for a perfect God.