Lying behind the secularization theory were two great assumptions: first, the theory assumes that theism is basically an inherited belief that is necessary to provide meaning, coherence, and comfort. In other words, secularization theory has an essentially functional understanding of religion. So, as religion’s function is no longer needed, as people find other sources of comfort and meaning in life, belief in God will recede.

Second, secularization theory assumes that the forms of religious belief were supported by the acknowledgment of its social functions. In other words, the adherents of secularization theory believed that religious forms would remain for some time even after true belief was gone—at least so long as people found them aesthetically attractive—but that eventually they also would disappear. They believed history was driving toward the utter removal of belief in God, and that education, technology, affluence, and the inevitable breaks with tradition that came with modernity would lead to a massive, civilization-wide loss of belief.

It would work this way: first it would become plausible or thinkable not to believe in God, and then eventually it would become inevitable that one would not believe in God at all. Secularization theorists believed education would play a big role in this, effecting in society an intellectual coming of age. In sum, belief in God was a part of prehistory, a part of what Nietzsche would call “the intellectual infancy of humanity.” But as humanity has now come of age, belief in God is no longer necessary. Freud put it this way: “The more the fruits of knowledge become accessible to men, the more widespread is the decline of religious belief.”¹³

Ultimately then, modernity would produce a fully secularized world. On a global scale it would begin in the West, where technology, scientific advance, and democratic theory had most quickly taken shape. But eventually these ideas would spread around the world, and secularization would be a global phenomenon. The theory certainly appeared to be credible, and it soon became the accepted wisdom. Indeed, it was considered to be inexorable: there would be a worldwide, global, secular culture, led by new institutions such as the United Nations and marked by the rejection of both the social functions and the symbolic nature of theistic belief.

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John Sommerville, another major British figure in secularization theory, suggested that secularization would follow this pattern: first would come the secularization of space. In the year 1500 in Great Britain, about half of all the land in the kingdom was owned by the church, and a good portion of the rest was owned by the Crown. That began to change with Henry VIII, who confiscated the monasteries and began the process of secularizing the property. The idea that land would not be owned by either the Church or the Crown was a massive change in British society. Second, Sommerville predicted the secularization of time and play, and third, the secularization of language. Fourth was the secularization of technology and work. No longer would people consider their vocation as being done to the glory of God. Rather, the dominant paradigm would be that of making a contribution to society and ultimately a profit. Then would follow the secularization of art, the secularization of power, the secularization of personhood and association, and finally the secularization of scholarship and science until humanity’s passage from infancy and adolescence into adulthood was complete.

Sommerville went on to speak of six aspects of secularization. First, secularization would take place at the macro-social-institutional level. This is known as differentiation. This process has clearly become a reality. Indeed, the fragmentation of knowledge and the specialization of expertise are now just taken for granted. Whereas the church once defined reality across an entire range of intellectual fields, it does so no longer— even for most Christians. We live in a time in which it is plausible to us that people would not ask the pastor about vocational issues, intellectual issues, legal issues, and all the rest. The church used to be at the center of all these questions, but differentiation now means that you go to a lawyer for legal advice and to a psychotherapist for counseling. People now go to any number of experts who are completely freed from the church and theistic belief. That is a massive shift brought about by secularization.