The changes that have taken place in religious and ecclesiastical life in Western Europe are characterised as a process of secularisation. Secularisation encompasses three different processes, namely a decline in the religiosity of people, the restriction of the range of influence of religion and the adaptation of religion to the values of society. By means of these processes on three levels the developments with relation to religious life in its entirety can be described. Since changes in religious life are connected with changes in society and the culture of the society in which that religion functions, a better understanding of what secularisation entails demands that we look at those developments in society which have promoted changes in religion and the church. Developments in society that are discussed include the changed organisation of society and processes of rationalisation, democratisation and subjectivation. Finally, it is shown how these developments resulted in the diminishing significance of religion and the churches in and for society.