Behind this public, or exoteric, aspect of al-Fārābī’s work stood a massive body of more properly philosophic or scientific inquiries, which established his reputation among Muslims as the greatest philosophical authority after Aristotle, a great interpreter of the thought of Plato and Aristotle and their commentators, and a master to whom almost all major Muslim as well as a number of Jewish and Christian philosophers turned for a fuller understanding of the controversial, troublesome, and intricate questions of philosophy. Continuing the tradition of the Hellenistic masters of the Athenian and Alexandrian philosophical schools, al-Fārābī broadened the range of philosophical inquiry and fixed its form. He paid special attention to the study of language and its relation to logic. In his numerous commentaries on Aristotle’s logical works, he expounded for the first time in Arabic the entire range of the scientific and nonscientific forms of argument and established the place of logic as an indispensable prerequisite for philosophic inquiry. His writings on natural science exposed the foundation and assumptions of Aristotle’s physics and dealt with the arguments of Aristotle’s opponents, both philosophers and scientists, pagan, Christian, and Muslim. The analogy of religion and philosophy
Al-Fārābī’s theological and political writings showed later Muslim philosophers the way to deal with the question of the relation between philosophy and religion and presented them with a complex set of problems that they continued to elaborate, modify, and develop in different directions. Starting with the view that religion is analogous or similar to philosophy, al-Fārābī argued that the idea of the true prophet-lawgiver ought to be the same as that of the true philosopher-king. Thus, he challenged both al-Kindī’s view that prophets and philosophers have different and independent ways to the highest truth available to human beings and al-Rāzī’s view that philosophy is the only way to that knowledge. That a person could combine the functions of prophecy, lawgiving, philosophy, and kingship did not necessarily mean that these functions were identical; it did mean, however, that they all are legitimate subjects of philosophic inquiry. Philosophy must account for the powers, knowledge, and activities of the prophet, lawgiver, and king, which it must distinguish from and relate to those of the philosopher. The public, or political, function of philosophy was emphasized. Unlike Neoplatonism, which had for long limited itself to the Platonic teaching that the function of philosophy is to liberate the soul from the shadowy existence of the cave—in which knowledge can only be imperfectly comprehended as shadows reflecting the light of the truth beyond the cave (the world of senses)—al-Fārābī insisted with Plato that the philosopher must be forced to return to the cave, learn to talk to its inhabitants in a manner they can comprehend, and engage in actions that may improve their lot. Impact on Ismāʿīlī theology
Although it is not always easy to know the immediate practical intentions of a philosopher, it must be remembered that in al-Fārābī’s lifetime the fate of the Islamic world was in the balance. The Sunni caliphate’s power hardly extended beyond Baghdad, and it appeared quite likely that the various Shiʿi sects, especially the Ismāʿīlīs, would finally overpower it and establish a new political order. Of all the movements in Islamic theology, Ismāʿīlī theology was the one that was most clearly and massively penetrated by philosophy. Yet, its Neoplatonic cosmology, revolutionary background, antinomianism (antilegalism), and general expectation that divine laws were about to become superfluous with the appearance of the qāʾim (the imam of the “resurrection”) all militated against the development of a coherent political theory to meet the practical demands of political life and present a viable practical alternative to the Sunni caliphate. Al-Fārābī’s theologico-political writings helped point out this basic defect of Ismāʿīlī theology. Under the Fāṭimids in Egypt (969–1171), Ismāʿīlī theology modified its cosmology in the direction suggested by al-Fārābī, returned to the view that the community must continue to live under the divine law, and postponed the prospect of the abolition of divine laws and the appearance of the qāʾim to an indefinite point in the future. The teachings of Avicenna The “Oriental Philosophy”
Even more indicative of al-Fārābī’s success is the fact that his writings helped produce a philosopher of the stature of Avicenna (flourished 10th–11th centuries), whose versatility, imagination, inventiveness, and prudence shaped philosophy into a powerful force that gradually penetrated Islamic theology and mysticism and Persian poetry in Eastern Islam and gave them universality and theoretical depth. His own personal philosophic views, he said, were those of the ancient sages of Greece (including the genuine views of Plato and Aristotle), which he had set forth in the “Oriental Philosophy,” a book that has not survived and probably was not written or meant to be written. They were not identical with the common Peripatetic (Aristotelian) doctrines and were to be distinguished from the learning of his contemporaries, the Christian “Aristotelians” of Baghdad, which he attacked as vulgar, distorted, and falsified. His most voluminous writing, Kitāb al-shifāʾ (“The Book of Healing”), was meant to accommodate the doctrines of other philosophers as well as hint at his own personal views, which are elaborated elsewhere in more imaginative and allegorical forms. Distinction between essence and existence and the doctrine of creation
Avicenna had learned from certain hints in al-Fārābī that the exoteric teachings of Plato regarding the forms, creation, and the immortality of individual souls were closer to revealed doctrines than the genuine views of Aristotle, that the doctrines of Plotinus and later Neoplatonic commentators were useful in harmonizing Aristotle’s views with revealed doctrines, and that philosophy must accommodate itself to the divine law on the issue of creation and of reward and punishment in the hereafter, which presupposes some form of individual immortality. Following al-Fārābī’s lead, Avicenna initiated a full-fledged inquiry into the question of being, in which he distinguished between essence and existence. He argued that the fact of existence cannot be inferred from or accounted for by the essence of existing things and that form and matter by themselves cannot interact and originate the movement of the universe or the progressive actualization of existing things. Existence must, therefore, be due to an agent-cause that necessitates, imparts, gives, or adds existence to an essence. To do so, the cause must be an existing thing and coexist with its effect. The universe consists of a chain of actual beings, each giving existence to the one below it and responsible for the existence of the rest of the chain below. Because an actual infinite is deemed impossible by Avicenna, this chain as a whole must terminate in a being that is wholly simple and one, whose essence is its very existence, and therefore is self-sufficient and not in need of something else to give it existence. Because its existence is not contingent on or necessitated by something else but is necessary and eternal in itself, it satisfies the condition of being the necessitating cause of the entire chain that constitutes the eternal world of contingent existing things.