Aristotle’s Theory of Active and Passive Intellect in De Anima

Aristotle’s De Anima Book III, chapter 5 (430a10–25) is one of the most concise yet profoundly influential passages in the history of philosophy. In fewer than twenty lines of Greek, Aristotle introduces the distinction between the active intellect (nous poiētikos) and the passive intellect (nous pathētikos), a distinction that has shaped subsequent discussions of human cognition, abstraction, and immortality for over two millennia.

The chapter addresses a problem left unresolved in III.4: if the intellect in its receptive capacity is originally like a writing tablet on which nothing is yet written, something must actualize its potentiality and enable it to think. Aristotle resolves this by positing two aspects within the intellectual soul. The passive intellect is capable of becoming all things; it is potential, receptive, and perishable. By contrast, the active intellect makes all things; it is separate, unaffected, unmixed, and essentially actuality itself. Aristotle compares its role to that of light, which renders potentially visible colors actually visible (Aristotle, 1984, 430a15–17).

When the active intellect is separated from the composite human being, it is solely what it intrinsically is, and this alone, Aristotle declares, is immortal and eternal. The passive intellect, however, perishes with the body, and because the active intellect is impassive, we retain no memory of its activity after death (Aristotle, 1984, 430a22–23).

This brief argument has generated radically divergent interpretations. Ancient commentators such as Alexander of Aphrodisias identified the active intellect with God or the Unmoved Mover, external to the individual soul. Themistius, by contrast, treated it as an immanent but transcendent power within each human being. In the Islamic tradition, Averroes defended the thesis of a single active intellect shared by all humanity, a position later condemned as monopsychism. Thomas Aquinas reconciled Aristotle with Christian doctrine by arguing that both intellects are faculties of the individual soul, with immortality belonging properly to the rational soul as a whole through divine grace rather than to the active intellect alone (Aquinas, 1268/1947).

Contemporary scholarship has largely moved away from theistic or externalist readings. Most interpreters now regard the active intellect as an intrinsic, if transcendent, aspect of human cognitive capacity, responsible for the abstraction of universal forms from sensory phantasmata (Caston, 1999; Shields, 2016; Burnyeat, 2008). The active intellect is thus the principle that makes scientific understanding (epistēmē) possible by illuminating the potentially intelligible content present in imagination.

De Anima III.5 therefore constitutes Aristotle’s deepest account of what distinguishes human intelligence from animal sensation: the presence of an eternally actual principle that enables finite, embodied beings to grasp immutable, universal truths. The brevity and deliberate ambiguity of the text have ensured its enduring vitality in philosophical debate.

References

Aquinas, T. (1947). Summa theologica (Fathers of the English Dominican Province, Trans.). Benziger Bros. (Original work written 1265–1274)

Aristotle. (1984). De anima (J. A. Smith, Trans.). In J. Barnes (Ed.), The complete works of Aristotle (Vol. 1, pp. 641–692). Princeton University Press. (Original work written ca. 330 BCE)

Burnyeat, M. F. (2008). Aristotle’s divine intellect. Marquette University Press.

Caston, V. (1999). Aristotle’s two intellects: A modest proposal. Phronesis, 44(3), 199–227.

Shields, C. (2016). Aristotle: De anima. Oxford University Press.