Susumu Shimazono, one of Japan's foremost sociologists of religion, deals with the development of popular religious and spiritual movements in Japan in the nineteenth and the twentieth centuries. At present, it is estimated that more than ten percent of Japan's total population are members of the so-called New Religions. While Buddhist and Shintoist influences remain pronounced, there are many other features common to modern Japan's popular religious thinking. Through a careful study of these features, the author examines classical concepts and theories of religious studies, proposes alternative approaches, and reconsiders religion in modernity in the context of Japanese cultural heritage.