One of the main issues that this book examines is the function of the mode of thought in conditioning Islamic legal opinion (fatwā). In its relation to religion, mode of thinking is reflected in groups’ perspective of religion including what aspects of religion are deemed significant and what are marginalized or overlooked. It is also manifested in how religious teachings are conceived and applied. While the mode of thought of groups may shift over time and may not be monolithic at any point in time, it is nonetheless possible to discern dominant modes of thought as manifested in ideas, views, opinions, and judgment held by the groups as they respond to their milieu as opposed to those that are marginal.

Three major modes of thought are relevant to this study, namely traditionalism, revivalism, and reformism. The meanings attributed to these terms must be clarified at the outset to avoid confusion as they have been used by various scholars in diverse ways. Against the backdrop of Indonesian Islam's complex diversity, these typologies of the mode of thought in understanding religious experience might be viewed as an oversimplification. However, such categorizations are ideal types which do not ignore the dynamic interaction within and between a particular social group's religious outlook while facilitating analyses of interplay and contestation among the variety of modes of thought. As ideal types, these constructions are also meant to capture the main tendencies of the mode of thought in the context of Indonesian Muslim society without over-generalizing. In general, Nahdlatul Ulama’ is widely associated with traditionalistic Islam as opposed to Muhammadiyah which is predominantly classified as an Islamic reformist movement. MUI, on the other hand, being the amalgamation of all Indonesian Muslim groups and supported by the state, is often highlighted for its traditionalistic and conservative bent in Indonesian Islam. The meaning of these modes of thought as defined in this thesis and their usage in analyzing legal opinion (fatwā) will elucidate the extent to which such dominant perceptions of their mode of thinking hold sway, although this in itself is not the major aim of the thesis.