Agent Intellect, The

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In his On the Soul, iii 45, Aristotle wrote that there is one intellect that becomes all things and another that makes all things, just as light makes colors visible. It is separate, impassible, unmixed, and in essence activity; it alone is immortal and eternal. Those few statements are the basis of the theory of the agent intellect.

Aristotle was studied with intense and sometimes imaginative care by ancient and medieval scholars, and his ideas were developed to the extent of dominating thought about human thinking. Our concept arose in Greek but was developed in Arabic and flowered in medieval Latin; "agent intellect" is the English rendering of the Latin intellectus agens, but behind that lie a number of other terms. Furthermore, English writers have sometimes used active instead of agent.

The field falls into three parts: the Greek commentators on Aristotle, the Arabic philosophers who developed his views, and the medieval Europeans who built on the rest. Aristotle himself was sparing with technical terms, and the text of On the Soul, iii 4 and 5. is in a poor state that raises several questions. Later thinkers brought in material from earlier parts of On the Soul (i 4, ii 2); part of On the Generation of Animals (ii 3) in which Aristotle says that in humans the intellect (unqualified) comes into the fetus from outside (thurathen ); passages from his ethics and his metaphysics, in which the intellect is regarded as in some sense divine; and the end of his Posterior Analytics (ii 19). The result is far from anything Aristotle can have held.

Aristotle's student Theophrastus raised pertinent questions about the agent intellect, reported, perhaps unreliably, by Themistius (c. 31788), who himself studied Aristotle with care and ingenuity. He reports one early viewthat the agent intellect was the body of premises and deductions that form knowledgebut dismisses it, as he does the view of Alexander of Aphrodisias (c. 200 CE), who held that the productive or active or agent nous (now identified with the nous thurathen that for Aristotle was a biological concept) was identical with the First God or the unmoved mover of Metaphysics XII 8. It is clear that there had been much discussion about this already, and already we see a tendency to the hypostatization of various intellects.

Themistius and Alexander together influenced Arabic thinkers. Most important are Avicenna (9801047) and Averroes (112698). Avicenna had a theory of celestial intellects, derived from Neoplatonist views as well as Aristotle's metaphysics and psychology; for him the agent intellect was the tenth and lowest of a chain descending from the First Intellect, far removed from the human soul. More accessible was Averroes's view, which started from Aristotle's distinction between intellect as potential and as active or agent but went on to argue that the agent intellect was one and the same in all men, leading on to the question whether the potential intellect was also one and the same in all men. The Arabic philosophers were also interested in this intellect as the source of prophecy, and in the possible conjunction with it of the human reason.

Arabic works were translated into Latin by Western medieval scholars, so that Europe became aware of much of Aristotle and of his Arabic interpreters at almost the same time; in the thirteenth century it was taken for granted that the words intellectus agens stood for something definite, but there remained many questions about it. Albert the Great (c.12001280) introduced the Latin expression intellectus agens. He got to know the Arabic evidence and dealt with the fourfold distinction of agent, possible, acquired, and speculative intellects, which became the basis for later discussion.

In his time there was an Averroist school of thought, particularly in Padua, which troubled more orthodox thinkers; even Thomas Aquinas (12251274) wrote against them. In his extensive writings he worked out a theory aimed at satisfying both Aristotelians and Christian theologians. He quoted Aristotle to disprove his opponents' views, using the Physics, On the Soul, and Themistius, Avicenna, and others. He was primarily concerned with whether there was but a single intellect for all men and the subsidiary question about the agent and the receptive intellects. In his Summa he concentrates on the internal features of the intellect, and the agent is that which by its light abstracts species from images.

A single agent intellect would not secure individual immortality as required by Christianity, and when many Averroist doctrines were condemned by the Church in 1277, a number were about the Agent Intellect. An anonymous work from the early fourteenth century covers sixteen supposed views about the agent intellect from Plato (who is said to have denied its existence) through the Arabs to a number of others; the writer favors Thomas Aquinas. An array of arguments, partly from Aristotle but partly independent, is deployed. There are questions about the existence of the agent intellect, and again about whether there is one in each person or only one for all, as there is one light source illuminating all illuminated objects.

Even in the Renaissance the concept is found in the Averroism of Pomponazzi (14621525): in his On the Immortality of the Soul he doubted immortality, but, opposed by the Church, argued that philosophy could not prove anything in this area. Zabarella (15331589), a logician, also still spoke of the agent intellect as playing a part in induction. Finally, Aristotle's dominance came to an end, and his account of the intellect has been described recently as a museum piece. Instead of his metaphysical approach, a scientific psychology slowly developed, which was not interested in analyzing his actual words.

See also Aristotle; Averroes; Pomponazzi, Pietro; Thomas Aquinas, St.


Davidson, H Alfarabi. Avicenna and Averroes on Intellect. Oxford: Oxford University Press 1992.

Huby, P. M. "Stages in the Development of Language about Aristotle's Nous." In Blumenthal and Robinson, Aristotle and the Later Tradition. OSAP suppl. vol.. Oxford: Oxford University Press 1991, 129143.

Kuksewicz, Z. "The Potential and the Agent Intellect." In Cambridge History of Later Medieval Philosophy. Cambridge, U.K.: Cambridge University Press, 1982.

Kurfess, H. Zur Geschichte der Erklärung der Aristotelischen Lehre vom sog. NOUS POIHTIKOS und PAQHTIKOS. Tübingen, 1911. Reprinted in Aristotle and His Influence, edited by L. Taran. New York and London: Garland, 1987.

Pamela M. Huby (2005)