This is the lecture by M.B. ter Borg upon accepting the Chair in Non-institutional Religion in Modern Society at the University of Leyden, Netherlands. He opens by outlining a theoretical model which explains why religion is a timeless phenomenon. He goes on to give an impression of the relationship between institutional and non-institutional religion. Then he suggests what the causes are of the growing importance of religion in modern society. He then uses the theoretical model to make it clear why this so-called comeback of religion is partly non-institutional. He then finishes by providing a few examples of non-institutional religion.