By the time Balaguer was conquered by the Christians in 1105, the Almoravids had been ruling in the Iberian Peninsula for almost two decades, and the Taifa kings of the Upper March had managed to hold out for a long time against direct occupation by the new Berber rulers. Islam possesses no hierarchical institution responsible for formulating the correct religious doctrine as per the Catholic Church. The task of interpreting the Revelation is in the hands of the 'ulama' or religious scholars, considered to be the "heirs" of the Prophet. The structure and characteristics of the world of Islamic knowledge generates divergent interpretations and differing versions of religious law. Criticism of The Revival of Religious Sciences in the Islamic West seems to have been connected first and foremost to the conviction that al-Ghazali had ended up being too accepting of the doctrines of the philosophers, of the Isma'ilis and the radical Sufis he had originally intended to refute.