I saw a video recently where Ravi Zacharias answered a student at Yale’s question, which was essentially, “Why can’t I just do good? Why do I have to become a Christian?”
And Ravi Zacharias answered the question, but I feel like he over-complicated it or at least expressed it in a more esoteric or indirect way than needed. There is a fairly direct answer to the question. It’s because no matter how good you are, you aren’t correcting the core problem humanity has.
God is life’s source. It’s something that every theist can comprehend. God was the originator of life and most theists will also agree man has an innate hunger for communion with God. Now, consider that almost every desire we have corresponds to some kind of need. We get hungry because we need food. We get tired because we need sleep. We long for God, because we don’t have Him. But the Bible explains why we don’t have Him. Because we choose to reject Him. We choose to supplant Him in our hearts with something, anything, and everything else. There is a relationship that is broken, but that relationship is with the source of life. So no matter what good deeds you do for others, it will never address that broken relationship. A hose with a break in it will never let water flow through, no matter how earnestly you point it in the direction of the flowers that need the water. Likewise, we have broken that vital connection to the source of life and our good intentions do not repair that.
Even more so, since the question doesn’t discount the Gospel as a truthful accounting, it merely calls into question whether we need to adhere to all the tenants of the Bible and Christian faith. If our root problem is a broken relationship with God, and He really did send His Son to die an excruciating and humiliating death for us; and you consider Christ’s claim to be The Way, The Truth, and the Life, assuring us no one gets to the Father except through Him (John 14:6), then how can we spit in God’s face and say, “No, no. You’re way isn’t needed. I know I can do it somehow. I’ll just do nice things.” I’ve been married long enough to know that doing something nice that ignores the issue between my wife and I is not going to help anything. Not to mention, the whole thing smacks of the very problem that started mankind’s rebellion. In Genesis, man is told don’t eat the fruit from one tree. Everything else is ok, but not that one tree. But man questioned God and said, “Nah. That tree is good too.”
We have to choose to stop putting ourselves as god in our lives and acknowledge, “God you’re right. I submit to You.” And we do that by accepting the sacrifice He provided in Christ. Then good works result. Then good works matter and are pleasing offerings before God. Everything else is just trying to enthrone self and that is never going to please the God Who spoke the vast universe into existence.