Thought of ‘Fikih Sosial’ Kiai Sahal Mahfudh is a method to explore and respond to the dynamics of law in society. ‘Fikih Sosial’ is a model of fiqh development based maṣlaḥah oriented with a clear manhaj. As an embryo of ‘fikih peradaban’ (civilizing fiqh), ‘Fikih Sosial’ was based on the method of the underlying ideas of Moslem scholars (‘ulamā’), not a product of their thoughts. Therefore, to follow the method, may result the same product and the different one as well. The method is to contextualize ‘traditional authoritative book’ (al-kutub al-mu’tabarah) through the undestanding of the applications of rules of uṣūl al-fiqh or qawā’id al-fiqhiyyah. The development of masālik al-'illah theory is also urgent in accordance with producing fikih based maṣlaḥah al-'āmmah. In this position, fikih Kiai Sahal completely answers the problem of the integration of authenticity and modernity which are often contradictory and antagonistic