Perhaps most intriguing and perplexing among Aristotle’s writings is his theory on how the human intellect passes from a non-thinking state to a thinking one. Aristotle assumed that human thought reflects reality in a distortion-free manner. He also assumed that inborn qualities would taint the thoughts acquired by the human intellect, thus preventing it from performing its proper function. As a result, he took the human intellect to be a “part of the soul” with the ability to “become each thing” but with no nature of its own (De Anima 3.4.429a 10, 21-22; 429b 6). Next, he argued for the presence in the soul, as in all things, of “matter” and a “cause” or “agent” which leads the matter from potentiality to actuality. Thus, Aristotle posited, alongside the potential or material intellect capable of “becoming all things” via the acquisition of all thoughts, an active intellect capable of “making all things” via the making of all thoughts. (De Anima 3.5.430a 10-15).
The meaning of potential intellect and active intellect and the relationship between them are not clear in Aristotle’s De Anima. Is the active intellect part of the human soul or separate from it? (Davidson 3-4). “If the active intellect is entirely independent of the body, how can we reconcile it with Aristotle’s prevailing view of soul as the form of body” (Bunnin and Yu 11-12)? These questions have perplexed philosophers, who have tried to answer them, for two thousand years. Among them were ancient Greek commentators, medieval Islamic, Jewish, and Christian philosophers, and European philosophers. Each of them carefully studied Aristotle, looking for the answers to these questions. In his writings they expected to find the key to man’s essence, his fate, and the structure of the universe (Davidson 3-4). I will demonstrate that the Averroist interpretation of Aristotle’s active intellect is most consistent with Aristotle’s system and, at the same time, that Aristotle is consistent with Plato on this subject, justifying the Neoplatonist interpretation of Aristotle.
There are three prevailing interpretations of Aristotle’s active intellect: Alexander’s, Averroes’, and Aquinas’ (Nash 111). Aristotle’s earliest followers seem in disagreement in their views on the active intellect. Theophrastus conceived of it as a part of human nature. Eudemus, described God as the active intellect in his Ethics. The philosophical opinions of other early Peripatetics and their interpretations of Aristotle are unclear on account of the scarcity of surviving evidence of them. It is, however, known that Theophrastus’ successor Strato and Theophrastus’ colleagues Aristoxenus and Dicaearchus denied all intellectual cognition and even the entire realm of the intellect (Brentano 4).
The Peripatetics of the first and second centuries A.D., on the other hand, held fast to the views of their founder and took it upon themselves to explain and defend them. Extant writings from this school are by Alexander Aphrodisiensis (Brentano 5). Alexander of Aphrodisias identified Aristotle’s active intellect with God (Nash 111). His interpretation of the active intellect is that it is “a purely spiritual substance, separate from the nature of man and acting upon him, the first ground for all things, the divine intelligence itself” (Brentano 5). Through its influence man acquires actual knowledge, while the capacity for receiving this influence depends upon a certain mixture of elements in the human body; hence he claims that the soul of man is wholly dependent upon the body in its thinking and being and is mortal (Brentano 5).
Others disagreed with Alexander and Theophrastus, arguing instead that the active intellect “should be identified with immediately known propositions and the truths that follow from them” (Brentano 5). This interpretation seems to be derived from connections made between the active intellect and passages from the last chapter of the Posterior Analytics and the Nicomachean Ethics. Themistius cited Theophrastus in criticizing both this interpretation and Alexander’s (Brentano 5).
The debate continued throughout the Middle Ages. The Arabs, who were connected to the Peripatetic School of Alexandria through the Syrians, were clearly influenced by Alexander Aphrodisiensis. Nevertheless, they were not in complete agreement with him. Specifically, Avicenna and Averroes concluded, like Themistius and Theophrastus, that the active and receptive intellects were immaterial. Avicenna followed in Alexander Aphrodisiensis’ footsteps in arguing that of the two intellects distinguished by Aristotle in chapter 5 of De Anima 3, the intellect that becomes all things, not the intellect that produces all things, is “found in man as its subject.” Thus, in Platonic fashion, “the sensory ceases to be the source of intellectual cognition” and “sensory representations are to constitute merely an occasion for our intellectual knowledge” (Brentano 6).
Averroes interpreted the active intellect as a cosmic principle of intelligence to which every human intellect is related (Nash 111). Averroes posits the two principles distinguished by Aristotle in chapter 5 of De Anima 3 as “two purely intellectual substances which are by nature distinct from man as sensitive being” (Brentano 12).
For Averroes, the active intellect and the human potential intellect were part of a greater cosmic scheme. The physical universe was made up of transparent celestial spheres with the stars and planets embedded in them rotating around a stationary sublunar world. Presiding over this cosmos is a first supreme being, an intellect consisting of pure thought. Averroes also posits other intellects or intelligences whose function is to govern the motion of the celestial spheres. The active intellect, which is the cause of human thought, is at the end of this chain of celestial beings. These intelligences, including the active intellect, and the celestial spheres themselves, come into being via eternal emanations originating from the First Cause (Davidson 4).
The active intellect was of great importance to Averroes, whose philosophy dealt extensively with it. In contradistinction to most scholastic philosophers, Averroes and the majority of medieval Islamic and Jewish philosophers were certain the active intellect was an incorporeal substance that transcended the human soul and held a definite position in the incorporeal hierarchy. He conceived of the active intellect as being responsible for leading the human intellect from potentially thinking to actually thinking and that it played an important part in human immortality (Davidson 4-5).
St. Thomas Aquinas identified the active intellect as something individual and particular in each human being (Nash 111). Aquinas’ explanation coincides with Theophrastus’ as paraphrased by Themistius. Aquinas takes both the active and potential intellects to be immaterial. He also takes them both to be part of human nature, and not purely spiritual substance. He explains that what Aristotle intended by saying that they are separate from the body is that “they do not have an organ like the faculties of the vegetative and sensitive part, but are found only in the soul as their subject” (Brentano 13).
Alexander’s and Aquinas’ interpretations of Aristotle’s active intellect are incompatible with the rest of Aristotle’s system. The problem with Alexander’s interpretation of Aristotle is that it requires an immanent God incompatible with the transcendent God of Aristotle’s Metaphysics. God would have to be immanently present in the world and “actively and personally involved in every act of human knowledge” (Nash 111) for Alexander’s interpretation to follow. Aquinas’ interpretation conflicts with the picture of humankind presented in Aristotle’s De Anima and is hard to reconcile with the rest of Aristotle’s system. Thus, even Roman Catholic thinkers reject Aquinas’s interpretation in favor of Averroes’.
The Averroist interpretation of the active and receptive intellects as immaterial, or as “two purely intellectual substances which are by nature distinct from man as sensitive being” (Brentano 12) is in agreement with the following three statements made by Aristotle in De Anima: (1) ” All, then, it may be said, characterize the soul by three marks, Movement, Sensation, Incorporeality, and each of these is traced back to the first principles.” (De Anima 1. 2. 405b10-13), (2) “Necessarily, the soul cannot be substance, except as form of a natural body that has life potentially” (De Anima 1. 5. 411b19-27), and (3) “the soul must be a ration or formulable essence, not a matter or subject” (De Anima 2. 2. 414a14-16).
The Averroist interpretation that of the two intellects distinguished by Aristotle in chapter 5 of De Anima 3, the intellect that becomes all things, not the intellect that produces all things, is “found in man as its subject” echoes Alexander’s interpretation of the active intellect, or as Alexander termed it “intellect from without,” and is in agreement with Aristotle’s statement in De Generatione Animalium regarding intellect “alone so to enter [the organism] and alone to be divine” (De Generatione Animalium 2.3.736b27-28).
In the Nicomachean Ethics, Aristotle stated that “the highest good is clearly something final” (NE 1. 5. 1097a28). Averroes’ interpretation of the active intellect as a cosmic principle of intelligence to which every human intellect is related (Nash 111) which is the cause of human thought, being at the end of a chain of celestial beings or intelligences emanating from the First Cause, is in agreement with the following statements by Aristotle:
“This world necessarily has a certain continuity with the upper motions; consequently all its power is derived from them. (For the originating principle of all motion must be deemed the first cause. Besides, that element is eternal and its motion has no limit in space, but is always complete; whereas all these bodies have separate regions which limit one another.)” (Meteorology 1. 2. 339a20-28).
Thus, the idea of the active intellect being entirely independent of the body is the only one that can be reconciled with Aristotle’s prevailing view of the soul as the form of body.
For Aristotle, “first cause” and “God” are synonymous. The following statement by Aristotle clearly illustrates his view of God as alike Averroes’ above: “And life also belongs to God; for the actuality of thought is life, and God is that actuality; and God’s self-dependent actuality is life most good and eternal.” (Metaphysics 1. 7. 1072b26-28). Averroes’ interpretation of the active cause as “in us” and responsible for moving us is in agreement with Aristotle’s statement that “It is clear, therefore that God is in the whole universe and moves everything, so, likewise God is in us and moves us” (Eudemian Ethics 7. 15. 1249b13-16).
Furthermore, Aristotle’s statement that “[Besides the mind that is potentially all things] there is another which is what it is by virtue of making all things: this is sort of a positive state like light; for in a sense light makes potential colours into actual colours. Mind in this sense of it is separable and impassable, unmixed, since it is in its essential nature actuality (for always the active is superior to the passive factor, the originating force to the matter which it forms.)” (De Anima 3.5. 430a14-19) contains language remarkably similar to Plato’s language in elucidating the Form of the Good in The Republic (Nash 111).
According to Plato, whose Form of the Good is widely accepted as synonymous with God, “The Good is the necessary condition of human knowledge. Without the Good, the world could not be intelligible and the human mind could not be intelligent. Just as light from the sun is necessary to turn potential color into actual color, so the light from the Good is necessary in order to make knowledge of the forms possible” (The Republic 505a-b). Thus, it appears that Aristotle’s active intellect (or God) corresponds with Plato’s Form of the Good (or God). Thus, of the three prevailing interpretations given, the Averroist, or Neoplatonic, interpretation is most consistent with Aristotle’s system (Nash 111).
That Averroes posits the active intellect as emanating from God may seem problematic at first since Aristotle’s theory doesn’t explicitly recognize emanation, but it is implicit in his theory. He clearly states that all motion is derived from the first cause, whose motion is unlimited in space (Meteorology 1. 2. 339a20-25); that God is in the whole universe, including in us, and moves everything, including us (Eudemian Ethics 7. 15. 1249b13-16); and that the active intellect alone enters us from without (De Generatione Animalium 2.3.736b, 28). Considering that for Aristotle “first cause” and “God” are synonymous, that the active intellect alone enters us from without and moves us from within, and that God is in us and moves us, “active intellect” must be either synonymous with “God” or a part of him. But for Aristotle, God has no parts, and neither does the active intellect.
The principle of emanation must be implicit in Aristotle’s system for it tomo be internally consistent. For Aristotle, the First Cause is transcendent and thus external to man. Yet it is also the source of all motion. The active intellect is external to man and yet “moves us from within”. The First Cause cannot be equated with the active intellect, yet as a motive force, must derive from the First Cause. Emanation explains how the active intellect can be external to us and yet moves us from within.
Brentano, Franz. The Psychology of Aristotle: In Particular His Doctrine of the Active Intellect. Berkeley: University of California Press, 1977.
Bunnin, Nicholas, and Jiyuan Yu. “Active Intellect.” The Blackwell Dictionary of Western Philosophy. Malden, MA: Blackwell Publishing, 2004.
Davidson, Herbert A. Alfarabi, Avicenna, and Averroes, on Intellect: Their Cosmologies, Theories of the Active Intellect, and Theories of Human Intellect. New York: Oxford University Press, 1992.
Nash, Ronald H. Life’s Ultimate Questions: An Introduction to Philosophy. Grand Rapids: Zondervan, 1999.