The paper considers the basic approaches and issues al-Ghazali's teachings about the reason and faith in the context of the ideal knowledge of the “golden period” of the classical Arab-Muslim philosophy. The basic approach to the understanding of al-Ghazali’s system was formulated by Ibn Rushd, who said that in al-Ghazali’s books he did not associate themselves with any of the exercises, being “with Ash'arites Ash’arites, with Sufis - Sufi, with philosophers - philosopher”. The problem of faith and reason is considered it from the point of view of kalam (“speculative theology”), fiqh (Islamic law) and Sufis. It is noted that a key reason for the understanding of his teachings as a system of metaphysics is the study, in which faith and reason complement each other on the field of knowledge, ie, it is a question of the unity of knowledge, both secular and religious.