If God does not exist, everything is lawful.

Jeff Jacoby:

"... What society loses when it discards Judeo-Christian faith and belief in G-d is something far more difficult to replace: the value system most likely to promote ethical behavior and sustain a decent society. That is because without G-d, the difference between good and evil becomes purely subjective. What makes murder inherently wrong is not that it feels wrong, but that a transcendent Creator to whom we are answerable commands: "Thou shalt not murder." What makes kindness to others inherently right is not that human reason says so, but that G-d does: "Love thy neighbor as thyself; I am the Lord."

Obviously this doesn't mean that religious people are always good, or that religion itself cannot lead to cruelty. Nor does it mean that atheists cannot be beautiful, ethical human beings. Belief in G-d alone does not guarantee goodness. But belief tethered to clear ethical values - Judeo-Christian monotheism - is society's best bet for restraining our worst moral impulses and encouraging our best ones.

The atheist alternative is a world in which right and wrong are ultimately matters of opinion, and in which we are finally accountable to no one but ourselves. That is anything but a tiding of comfort and joy."

Source: Jeff Jacoby