The rationalism of medieval Jewish philosophy is manifest in its doctrines of intellect. Seen as both an incorporeal, universal heavenly substance and as a personal psychic faculty, intellect is both within man and without; it is viewed as the source and goal of all knowledge, man's bridge to the upper world and to everlasting happiness.
The creative aspect of intellect is concentrated in a heavenly substance, which is regarded as the place of all universal ideas. It is called Intellect or Mind in the neoplatonic tradition (see *Neoplatonism) and Agent or Active Intellect in the Aristotelian (see *Aristotle and Aristotelianism), where it is the last of ten such intelligences and responsible for the
Man's intellect is related to this heavenly substance as a further emanation or individualization of universal Intelligence. Thinking is viewed as a process whereby the individual intellect and the object of intellection are both "illuminated" by the "light" of the universal intellect, leading to knowledge of the ideas latent in objects of our perception. Man's intellect thus "recreates" the intelligibles underlying all reality, bringing them and himself from potentiality to actuality. During intellection, the subject becomes one with its object, intellect becoming its intelligible (as said of Aristotle's Unmoved Mover, or God, in Metaphysics, 12:9, 1074b 34; and see On the Soul 3:4, 5). The philosophers prefer to call this relation "conjunction" (Arabic ittiṣāl, Hebrew devekut) rather than "union," which is the mystics' term, emphasizing thereby its impermanent nature and the retention of individuality by man and, particularly, by the universal Agent Intellect. The total, transcendent nature of the latter is generally considered beyond man's comprehension. Among the ideas that man can know for a certainty are self-evident principles of reason, or the laws of logic, and the rational structure of the world. They lead man to the knowledge of God's existence and His relation to man and the world. Such ideas place even relatively simple religious belief in an intellectual framework. Religious teachings are then seen as either obviously or ultimately rational, and the intellect to a large degree becomes the arbiter of faith (see particularly Saadiah Gaon, The Book of Beliefs and Opinions, introd. 5; 2:13; 3:1–4).
Human intellect is analyzed as a faculty of the soul and regarded as one of the internal senses. It is that which receives the already semiabstracted perceptions, known as phantasms, from the soul's intellectually disposed imagination or memory, and brings the process of abstraction and generalization to completion. The explanation of the process of disengagement from matter is facilitated for the later philosophers by their subdivision of the Aristotelian concept of active and passive states of intellect into a number of stages. Chief among these are the "hylic" (material), or "potential," intellect, viewed either as an incorporeal substance (following *Themistius) or as a disposition of the body to receive intelligibles (following *Alexander of Aphrodisias); the intellect "in act" and its counterpart, intellect "in habitu," which express an intellect that has become under the influence of the Agent Intellect actual and experienced; and the "acquired" intellect, representing intellectual perfection and conjunction with the world of eternal substances (a world also identified with the angelic realm; see F. Rahman's summary of the influential views of al-Fārābī and Avicenna, Prophecy in Islam (1958), 11–29; and see Levi ben Gershom's survey, Milḥamot ha-Shem, Part I).
Philosophers disputed whether this last stage can be reached by natural processes and whether personal identity is retained in it, vital issues relating to man's happiness and immortality. Despite opposition from traditional circles, the trend toward acceptance of a unified intellect and the loss of individuality in intellection, discernible in the thought of the Muslim philosopher Ibn Bājjah (see *Avempace) and of *Maimonides (see Guide 1:72; 74, 7th method), is pronounced in the writings of the Averroists. For *Averroes, whose influence upon such late figures as *Moses of Narbonne and *Levi ben Gershom was great, the potential intellect is a disposition of the Agent Intellect itself, only accidentally related to imaginative forms and man. Conjunction of the acquired intellect with the Agent Intellect, therefore, is seen as possible even in this life, and even though man, as commonly understood, thereby surrenders himself to universal being.
A. Altmann, in: H.A. Wolfson Jubilee Volume, 1 (1965), 47–87; I. Efros, in: JQR, 33 (1942/43), 133–70; O. Hamelin, La théorie de l'intellect d'après Aristote et ses commentateurs (1953), 3–72; A. Ivry, in: JAOS, 86 (1966), 76–85; H.A. Wolfson, in: Journal of the History of Ideas, 22 (1961), 3–32; Guttmann, Philosophies, index S.V. Intellect. ADD. BIBLIOGRAPHY: H. Davidson, Alfarabi, Avicenna and Averroes on Intellect (1992); Sirat, History of Jewish Philosophy in the Middle Ages (1985), index S.V. Intellect; D. Schwartz, "The Quadripartite Division of the Intellect in Medieval Jewish Thought," in: JQR. 84:2–3 (1993–94), 227–36; R. Jospe, Torah and Sophia: The Life and Thought of Shem Tov ibn Falaquera (1988), ch. 4.