Al-Ghazali on the Lawful and the Unlawful : Book XIV of the Revival of the Religious Sciences [Ghazali Series] By Abu Hamid Al-Ghazali. The main support for this application, especially in matters that are unclear, is caution or prudence, and Ghazali explains the degrees of prudence necessary, beginning with the prudence of the upright and ending with the prudence of the saintly.