"How then can a man be righteous before God? How can one born of woman be pure?"
We all on some level are aware of the presence of sin, and the need for some cosmic reconciliation. This need drives the person to acts of altruism and generosity, and has been the sentiment of spiritual inefficiency responsible for the world's religion in the first place. We subconsciously crave reconciliation and to prove ourselves as good people, because the immortal souls that we are recognize the desire for God, the presence of sin, and the spiritual validation that we require to nullify the second and satisfy the first. This can only come from Christ. Without Him, all your goodness and service (albeit beneficial to mankind) achieves you nothing but the same grave as the unrepentant murderer.