This chapter focuses on Max Weber’s thesis concerning the relationship between Calvinist Protestantism and the development of capitalism and describes fundamentalist thought and contrast it with mainstream Islam in order to construct an ideal type of fundamentalist doctrine. It discusses the criticism of Weber’s idealistic view but pointing out that a certain tradition in Islam—namely Sunnite fundamentalism of the eighteenth and nineteenth centuries—offers a number of striking resemblances to sixteenth- and seventeenth-century Calvinism in that it promoted innerworldly asceticism, rationalism and austerity. An authoritative interpretation of Weber’s studies on world religions holds that they must be regarded as a series of experiments through which Weber sought to show that the religious factor was crucial in the development of capitalism. Throughout Islamic history there have been scholars and preachers who, with an appeal to the core notions of Islam, that is, the dogma of God’s unity and the example of the Prophet, have militated against the religious and political status quo.