With deep interest I have followed the Indonesian people's fight for freedom and independence from 1945 onwards. This interest has come to be centred in particular on the question of how religions, especially Islam, were involved in this struggle, and what role they would fulfil in the new Indonesia. After having lived and worked in Indonesia from 1946 to the end of 1960, I was twice more enabled to visit Indonesia thanks to grants from the Netherlands Foundation for the Advancement of Tropical Research (WOTRO). It was during these sojourns in particular, from May to October 1966 and from February to July 1969, that the material for this study was collected, supplemented and checked. For the help I received during these visits I am greatly indebted to so many Indonesian informants that it is impossible to mention them all. Moreover, some of them would not appreciate being singled out by name. But while offering them these general thanks I am thinking of them all individually. In spite of all the help given and patience shown me, this publication is bound to be full of shortcomings. An older Muslim friend, however, once encouraged me by reminding me that perfection belongs only to God (al-kamäl li'lläh). Nevertheless, I should like to offer my apologies for errors and mistakes; I would appreciate it if readers drew my attention to them.