The first premise is that the propensity to sin is in man’s nature. In other words, selfishness, acquisitiveness, lust, and greed are part of who we are as humans. I think Darwin would have agreed with this. Indeed the Darwinian portrait of man is a remarkable corroboration of the Christian doctrine of original sin. Darwin’s unflattering view of man is much more realistic and accurate than Rousseau’s naïve view that man is by nature good and society is responsible for his problems.

Darwin understood that man is closer to the beasts than to the angels. In some ways man is worse than the animals because they simply do what comes naturally, while man sins willfully and deliberately.

So man must pay the wages of sin, and the wages of sin is death. This is the second premise of Christianity. The Bible equates death in the biological realm with sin in the moral realm. Some people will find this unduly harsh, but let me show why it is duly harsh. Sin structures our personalities and defines our thoughts and behavior. Sin is built into our habits so that we sin routinely, almost unthinkingly. Sin is not peripheral to humans, something we occasionally do, but is much more intrinsic to our identities. So does sin deserve a heavenly reward? Should God, who is eternally just and holy, compromise that justice and holiness and offer us salvation despite our hatred for Him and our desecration of His laws? It seems only fair that we who sin both against God and man should pay for our sins. This means that sinners cannot enter the kingdom of God.

How, then, are we to have salvation? For most religions, man must take the active role. Hinduism and Buddhism offer solutions that are remarkably similar: Through meditationwe confront our selfish desires and recognize that the “self” is the core of the problem. So we strive, in various ways, to eliminate this self and achieve its extinction. In effect, we seek to become nothing. We can advance toward this goal not merely through meditation but also through disciplined self- renunciation: renunciation of possessions, renunciation of sensual pleasure, and so on. This is a supremely difficult project. Among Buddhists only the monks claim to even approach nirvana. I believe the awareness of the chasm separating holiness from human weakness has produced, in Hindu and Buddhist cultures, their distinctive fatalism. Many Hindus believe fate will decree whether they reappear as a prince, a dog, or a flea in the next life.

Judaism and Islam offer a different formula, although they lead their adherents down the same path. Judaism and Islam are religions of law. Both have elaborate rituals and codes: Pray five times a day. Pack up and go to Mecca. Sacrifice a lamb or a goat. Wear a long beard. Keep kosher. The great Jewish jurist Maimonides even argues that circumcision is essential for salvation: “Whoever neglects the covenant of our ancestor Abraham and retains the foreskin … will have no portion in the world to come.” The rigor of these rules has caused many Jews and Muslims to ignore many of them and simply follow a select few prescriptions they can live with. These are the “reformed” Jews and Muslims, who seem to have given up trying to live up to the full rigor of their legal codes. They are basically living in hope that God is not a stickler for details.

But God is not a lenient tradesman willing to accept 30 percent payment; His justice demands full reimbursement. Still, it is hard not to sympathize with the slackers. They are actually correct that it is too difficult to render adequate recompense to God. I even sympathize with Christopher Hitchens, who complains that if God wanted man to live up to these high standards, “he should have taken more care to invent a different species.” Christianity agrees with Hitchens that the standards are difficult. Indeed Christianity says they are more than difficult; they are impossible. Not only is it impossible to stop sinning—even the most devout Christians cannot stop sinning— but it is also impossible to atone for one’s past sins. How would you go about atoning for them? Can you locate everyone you have wronged and make them whole? Yes, you can resolve to live a subse- quent life of goodness, but this is no atonement; you should be doing this anyway.