Most versions of secularization theory expect advanced modernity to weaken religion. In contrast, this chapter argues that two different dimensions of contemporary society affect religion in opposite ways. Rising levels of human security and well-being are assumed to drive towards religious decline, while growing cultural diversity is assumed to push towards religious growth. These two hypotheses are simultaneously investigated, using world wide data for 50 000 respondents from 37 countries with a predominantly Christian heritage. As dependent variables, two dimensions of religious involvement which relate to two core aspects of secularization theory are analyzed: church-oriented religious involvement and preferences for a religious impact on politics. The findings from three different analytical strategies demonstrate that each of the two religious orientations is positively related to the cultural diversity, and also that each of them is negatively related to human security and well-being. Furthermore, the results also indicate that the religious changes which took place between 1981 and 1999/2000 are negatively related to human well-being and security, and positively to cultural diversity. Thus, a set of comprehensive analyses of one and the same set of world wide data indicate that human security and cultural diversity affect religious involvement in opposite ways. It seems too simplistic, therefore, to view modernization as a universal cause of religious decline.