In our current era of holy terror, passionate faith has come to seem like a present danger. Writers such as Richard Dawkins, Sam Harris, and Christopher Hitchens have been happy to throw the baby out with the bathwater and declare that the danger is in religion itself. God, Hitchens writes, is not great.

But man, according to George E. Vaillant, M.D., is great. In Spiritual Evolution, Dr. Vaillant lays out a brilliant defense not of organized religion but of man’s inherent spirituality. Our spirituality, he shows, resides in our uniquely human brain design and in our innate capacity for emotions like love, hope, joy, forgiveness, and compassion, which are selected for by evolution and located in a different part of the brain than dogmatic religious belief. Evolution has made us spiritual creatures over time, he argues, and we are destined to become even more so. Spiritual Evolution makes the scientific case for spirituality as a positive force in human evolution, and he predicts for our species an even more loving future.

Vaillant traces this positive force in three different kinds of “evolution”: the natural selection of genes over millennia, of course, but also the cultural evolution within recorded history of ideas about the value of human life, and the development of spirituality within the lifetime of each individual. For thirty-five years, Dr. Vaillant directed Harvard’s famous longitudinal study of adult development, which has followed hundreds of men over seven decades of life. The study has yielded important insights into human spirituality, and Dr. Vaillant has drawn on these and on a range of psychological research, behavioral studies, and neuroscience, and on history, anecdote, and quotation to produce a book that is at once a work of scientific argument and a lyrical meditation on what it means to be human.

Spiritual Evolution is a life’s work, and it will restore our belief in faith as an essential human striving.