Michael Gerson argued that morality makes no sense without God: that there is no reason to do good rather than evil if God does not exist. Christopher Hitchens “responded” in his customary manner, by aggressively not getting the point, instead writing as though Gerson had written that “religion always makes people behave better than non-religious people,” which would clearly be insane. But the emptiness of Hitchens’s response does not make Gerson’s point valid.
An account of morality could be given that is consistent with a non-theistic religion, or even types of atheism. What renders atheism incompatible with a coherent account of morality, when it is incompatible, is physicalism (or what is sometimes described as reductive materialism). If it is true that the universe consists entirely and without remainder of particles and energy, then all human action must be within the domain of caused events, free will does not exist, and moral reasoning is futile if not illusory (as are other kinds of reasoning). Whether Hitchens’s atheism logically commits him to these views would require me to actually read his book, which neither his other commentaries on religion nor the reviews of his book give me any great incentive to do.