There is no denying that compared to the heydays of the 1950's, traditional Christian religion has meanwhile declined significantly and lost much of its former dominance, appeal and legitimacy, particularly in Western-Europe. Secularization theorists show convincing explanations for this downward trend, but however useful and valuable these explanations have been for the sociology of religion, this dissertation argues that the discipline's traditional obsession with secularization theory also has a massive downside. By placing this theory on a pedestal, it has been overshadowing (or obfuscating) other important developments that have meanwhile been taking place in the religious landscape of the West. Noteworthy are the increase in spiritual self-identifications as well as the expansion of a post-Christian 'New Age' spirituality. This dissertation argues that secularization theory's ascendancy in the sociology of religion has thwarted - intentionally or not - the social-scientific study of these two developments, thereby limiting the discipline's progress. Specifically, this unwanted situation has resulted in four neglected key issues which are explicated in the dissertation's introduction. The first problem is directly tackled in that first chapter. The other three issues are addressed as best as possible in the subsequent four empirical chapters.
The first key issue concerns the commonly held misconception that post-Christian 'New Age' spirituality is culturally incoherent (i.e., those concerned do not share a particular worldview) and socially and publicly insignificant (i.e., it has no influence whatsoever beyond the private domain). The dissertation's introduction explicates and critically evaluates both of these claims in the light of both recent and older scholarly works (both theoretical and empirical) originating from a more specialized literature on post-Christian 'New Age' spirituality. A thorough examination of the latter in fact reveals 1) a solid set of logically interrelated ideas that are central to the worldview of post-Christian 'New Age' spirituality (thereby defusing the first claim), and 2) that this type of spirituality is both socially transmissible and present in the public sphere (thereby defusing the second claim).
The second key problem pertains to the discipline's traditional focus on studying religious decline rather than religious change. Chapters 2 and 3 address this shortcoming by examining both processes in tandem. This is important because studying them separately merely provides one-sided views of how the religious landscape of the West has evolved over time. Chapter 2 therefore tests the thesis of religious decline, central to secularization theory, alongside theories of religious change that assert something completely different, namely that religion in Western-Europe has not so much declined but rather changed profoundly (i.e., from a traditional Christian religiosity toward a post-Christian 'New Age' spirituality). Chapter 2 finds support for both of these processes. Religion has declined, whether one understands it narrowly as traditional Christian religiosity, or more broadly so that it also includes new forms of religiosity and spirituality (like New Age). Noteworthy, the former has declined at a much higher pace than the latter. Although the rise of these new forms of religiosity and spirituality cannot compensate for the loss in traditional Christian religiosity, they do make up an increasing portion of the overall declining religious pie. Those who continue to be religious or spiritual deviate increasingly from the traditional Christian model, so when one does encounter religiosity, it is much more likely to be non-traditional religiosity (like New Age) than was true in the past, indicating a process of religious change. Chapter 3 then studies to what extent the decline of traditional Christian religion is responsible for religious transformations, both within and beyond Christian religion. More specifically, it systematically explicates and critically tests two theories on religious change that are both derived from Grace Davie's well-known and much-debated 'believing without belonging' thesis. Strikingly, the findings do not reinforce the typically foregrounded version of 'believing without belonging' (i.e., a de-institutionalization of Christianity), however, they do support the typically unnoticed version of a spiritualization of religion.
The third key issue has to do with the emergence and expansion of a research tradition on spiritual (and religious) self-identifications. It consists of scholars studying from scratch what people actually mean when they say they are spiritual (but not religious), thereby overlooking a whole body of specialized literature that explains what this spirituality may be all about (i.e., the clearly distinct and pre-existing research tradition on New Age spirituality). Chapter 4 closes this gap by connecting these two traditions, thereby stimulating a much-needed critical intellectual dialogue between the two areas of expertise. It does so by studying whether the 'spiritual but not religious' embrace New Age spirituality, and whether they much like New Agers dismiss traditional Christian religion, whereas the 'both religious and spiritual' adhere to traditional Christian religion and understand spirituality in a non-New Age fashion (i.e., spirituality in a Christian sense). Chapter 4 yet finds that the 'both religious and spiritual' generally have no less affinity with New Age spirituality than their non-religious counterparts. This is because the more liberal and progressive Christians in the former category embrace New Age spirituality, too, while their more conservative and traditional Christian counterparts in this former category rather dismiss it. Thus, spiritual self-identifications have become quite reliable shortcuts, both within and beyond Christian religion, to identify sympathy with New Age spirituality with.
The fourth and final key problem concerns the neglect of key issues within the social-scientific study of spirituality itself such as the infamous and obstinate 'New Age gender puzzle', i.e., the recurrent - but not yet satisfactorily explained - observation that far more women than men take an interest in New Age spirituality. Chapter 5 addresses this puzzle by systematically testing - for the first time - a theory that has been proposed nearly two decades ago by Heelas and Woodhead (2005). With their subjectivization thesis, they introduced contrasting and allegedly gendered notions of autonomous selfhood, viz., individuated- and relational subjectivism. They argue that men more typically endorse the former that fails to spur spiritual longings whereas women more naturally embrace the latter that does do so. Chapter 5 shows that women have indeed more affinity with New Age spirituality than men because they generally embrace relational subjectivism to a greater extent, thereby supporting the theory and contributing to the puzzle's solution.