Today,” he describes his views of modern religions and their potential for good and evil. In all three parts he approaches religion from the viewpoint of a philosopher who is convinced of evolutionary biology’s explanatory power with regard to both living organisms and human cultures. Just as neo-Darwinians discovered the significance of genes for understanding the fitness of various life-forms, so, too, have such social Darwinians as Dennett and Richard Dawkins emphasized the importance of memes in understanding how religious and other cultural ideas are created, copied, and transmitted. Memes can be ideas, beliefs, words, attitudes, styles, customs, tunes, strategies, and other elements of culture. For both genes and memes, information is passed from generation to generation, but the meme’s transmission is nongenetic.

In fact, so many differences exist between genes and memes that critics of Dennett and Dawkins have pointed out that any analogy between genes and memes is bound to be ambiguous, unclear, and unhelpful in explaining the mechanisms of cultural evolution. For example, memes, unlike genes, can be transmitted to nondescendants. Despite these criticisms, Dennett feels that the mimetic approach bolsters his analysis of religion. Indeed, he thinks that religions may be “culturally evolved parasites” whose evil ideas are unknown to their hosts. He sees some religions as malignant features of human culture, best dealt with by isolation, education, or eradication.

In the history of the Earth, religion appeared late in the evolution of Homo sapiens. However, once religion developed, it quickly diversified and spread; Dennett estimates that, over the millennia, more than a million religions have existed. Why were religions so popular? Scholars have suggested several of their uses: to provide comfort in times of suffering and distress, to give meaning to life, to mitigate the fear of death, to explain the inexplicable, and to encourage group solidarity in the face of enemies or threats. Dennett, for his part, believes that humans do not yet know the answer, but he thinks that science can help humankind to discover the answer. For example, the diversification and survival of certain religions might be explained in terms of a Darwinian competition among belief systems in which the “fittest” succeed and those unable to generate and retain followers fail.

Primitive religions were animistic, seeing spiritual agents in stones, storms, and animals. Eventually this animism developed into a belief in gods whose activities were interpreted by shamans. When such early religions (Dennett calls them “folk religions”) evolved into organized religions, dogmas that were immune to disconfirmation developed. For Dennett, no organized religion lacks dogmas, and a dogma-less belief system cannot really be a religion.

Market forces played a role in what Dennett calls the domestication of religion, a dynamic process in which leaders adapted religions to changing conditions. One important aspect in the transition from folk to organized religions is the “belief in belief.” This sort of belief is only possible in a mature religion, which is able to tolerate those who do not genuinely believe in the divine. (Instead, they believe that they should believe in God.) These believers in belief think that religion is useful for society even if it is not strictly true. Indeed, according to Dennett, many religious people are actually atheists in the sense that Jews are atheist with regard to Baal, Christians are atheist with regard to Apollo, and most believers are atheist with regard to the many gods in which humans have, in the past, believed. Obviously, all religions do not have the same beliefs, but for Dennett the success of religion depends not on uniformity of belief but uniformity in professing beliefs.

Theologians, such as Thomas Aquinas, who have tried to establish God’s existence rationally have failed, but what of those who have tried to justify their faith in God by love? For example, Mircea Eliade, the great scholar of religions, insisted that religious phenomena can be grasped only from the inside, not through outside (objective) analysis. Dennett calls this approach “pre-emptive disqualification,” and he strongly believes that such scholars are wrong in limiting the investigation of religion to the truly religious.

Recently, some scholars have tried to put certain religious beliefs to objective tests, for example, by experiments in the effectiveness of prayers in healing the sick. So far, these tests have generated mixed results. Dennett has a negative opinion of investigations to determine whether religious people are more moral than atheists because, in his view, any relationship between spirituality and moral goodness is an illusion. The values that he holds sacred are rooted in Enlightenment rationalism and Darwinian natural selection. He wants his readers to accept and spread his Darwinian message, which he believes will help stop the degradation of the environment and mitigate many foibles of human nature. He wants to protect democracy from those with religious agendas, and he proposes as his central policy recommendation the scientific education of all the world’s people.

As expected by Dennett and his publisher, Breaking the Spell generated controversy. Reviewers in religious journals accused Dennett of misunderstanding the unique nature of religious experience, in which the interpersonal encounter between believer and Revealer plays a pivotal role. Furthermore, Dennett did little to camouflage his hostility to religion, even though he claimed to be engaged in disinterested analysis. It was clear to many religious readers, whom Dennett explicitly targeted, that he believes that a religionless world would be a better place than one under the spell of numerous religions.

What was unexpected by Dennett were the negative reviews in secular and liberal journals. For example, Leon Wieseltier, literary editor of The New Republic, reviewed Breaking the Spell for The New York Times Book Review and accused Dennett of such a crude form of scientism that his book was as superstitious as many of the religions he attacked. Scientism can mean a doctrine holding that scientific methods can and should be applied to all fields of inquiry, but it can also mean making a religion of science. Breaking the Spell exhibits both these meanings. Dennett and his disciples responded to what they characterized as a “right-wing attack” on his book by reemphasizing their major contention that science, unlike religion, is a matter of evidence, not belief. Those sympathetic to Wieseltier’s views answered that many modern spells remain to be broken, including those generated by atheistic rationalists.

Science and religion are two important ways that humans understand their lives, their societies, and the universe. Both come with powerful emotional underpinnings, as the controversy over Breaking the Spell reveals. Throughout history both religious and atheistic ideologies have caused great harm, but it is easy to find examples of both religious believers and atheistic humanists who have done great good. On the other hand, despite the claims of Dennett, questions about the ultimate roles of science and religion in human life are not scientific questions. Both science and religion can and should be understood from both the outside and the inside. Because of the traditional antagonism between science and religion, such an integrated approach to bridging what, to some, seems unbridgeable will be difficult, but the dangers of exacerbating the hostility between these important determinants of human life and meaning could be devastating to human beings, which evolution has shown to be a very fragile species.