‘Without this nothing thinks’: The Enigma of the Active Intellect


The Anatomy of the Brain, Explained in a Series of Engravings, Charles Bell, 1802.

by Michael Munro

There is perhaps nothing more enigmatic in the history of philosophy than that which in the tradition is known as the active intellect (nous poiêtikos, al-‘aql al-fa‘‘āl). The few dense, cryptic sentences in which Aristotle gives it its inaugural formulation, which comprise the whole of the fifth chapter of book three of the De Anima, are on one scholar’s estimation the “most intensely studied sentences in the history of philosophy.”[1] The “obscurity and extreme brevity” of “this half-page chapter,” notes another, “are notorious.”[2] In light of that chapter’s posterity, what is it that so many have so intently sought to think by way of it?

The chapter in question (430a10-25) reads in full:[3]

Since in all of nature something is the matter for each genus (and this is all those things in potentiality), while something else is their cause and is productive (poiêtikon), by producing them all as a craft does in relation to the matter it has fashioned, necessarily these same differentiations are present in the soul. And one sort of mind exists by coming to be all things and one sort of mind exists by producing all things, as a kind of positive state, like light. For in a certain way, light makes colors existing in potentiality colors in actuality.

And this mind is separate and unaffected and unmixed, being in its essence actuality. For what produces is always superior to what is affected, as too the first principle is to the matter.

Actual knowledge is the same as the thing known, though in an individual potential knowledge is prior in time, though it is not prior in time generally.

But it is not the case that sometimes it thinks and sometimes it does not. And having been separated, this alone is just as it is, and this alone is deathless and everlasting, though we do not remember, because this is unaffected, whereas passive mind is perishable. And without this, nothing thinks.

However redoubtable may be the exegesis that this passage has not ceased to require, the scholarly consensus as to its general characterization can be simply put. Christopher Shields has done so expertly:

1. Aristotle introduces a division into mind (nous) which he maintains is present generally in nature, between the active and the passive (DA 430a10–14).

2. The active mind is compared to a craft, while the passive mind is likened to matter (DA 430a12–13).

3. The active mind is compared to light, which in a certain way makes colours that exist in potentiality exist in actuality (DA 430a16–17).

4. Having been separated, the active mind alone is deathless and everlasting (DA 430a23–24).

5. Passive mind, by contrast, is perishable (DA 430a24–25).

6. Because the active mind is unaffected, we are not in a position to remember—something or other at some time or other. Unfortunately Aristotle does not specify what exactly we cannot remember or when (DA 430a23–24).

7. Without this (this = either the passive mind or the active mind), nothing thinks—or one thinks nothing (DA 430a25).

“To the degree that there is agreement about these general claims,” Shields comments, “there is commensurate disagreement about how each is to be understood and developed.” The chapter’s striking last line is here exemplary.

The ambiguity of the last claim provides a useful illustration of the sorts of difficulties we encounter when we approach De Anima iii 5 for careful study: in the phrase (‘without this nothing thinks,’ or ‘without this x thinks nothing’; aneu toutou outhen noei; 430a25), one cannot even be sure about the intended referent of the demonstrative ‘this’ (touto) or about whether ‘nothing’ (outhen) is the subject or object of ‘thinks’ (noei). Thus, depending upon how it is construed, Aristotle’s Greek can be understood in at least four different ways: (i) without the active mind, nothing thinks; (ii) without the active mind, the passive mind thinks nothing; (iii) without the passive mind, nothing thinks; and (iv) without the passive mind, the active mind thinks nothing. These possibilities are not idle: we find different commentators understanding Aristotle’s text in these markedly different ways. Each interpretation seems justifiable in its own terms, and so none is indisputably to be preferred over its competitors, at least not on narrowly linguistic grounds. Interpretive questions thus begin without firm textual data. What holds for this single phrase iterates through the entire chapter.

“Consequently, although some progress is to be made by minute philological analysis of De Anima iii 5,” Shields concludes, “the text as it stands leaves unanswered many of the questions with which we began.”

As it stands there is yet one point on which the text admits no dispute: what is at issue in that text’s every interpretation remains “the act of thinking within thought itself.”[4] “To think does not mean merely to be affected by this or that thing, by this or that content of enacted thought,” Giorgio Agamben has written, “but rather at once to be affected by one’s own receptiveness and experience in each and every thing that is thought a pure power of thinking.”[5] “The experience of thought that is here in question,” in other words, Agamben continues, “is always experience of a common power.”[6] It is none other, and no less, than the commonality of that power that makes of the active intellect an enigma. Daniel Heller-Roazen has isolated the two components all enigmas share: “opacity and the hidden principle of their interpretation. That summary may appear willfully paradoxical,” Heller-Roazen comments, “yet enigmas verify its truth”: Were an enigma “immediately intelligible, it would be none at all,” yet were an enigma “solely solvable by means of knowledge extrinsic to its construction, it, too, could hardly be called an ‘enigma.’”[7]

The sense in which the active intellect constitutes an enigma is now clear. “The enigma can be solved only when the one who hears it knows that it turns, allusively, yet systematically, back upon itself.”[8] The intellect attains its activity only when it “turns,” with the decisive lucidity of the one whom it traverses, “allusively, yet systematically, back upon itself”: the intellect distinguishes itself in its immemorial craft by the activity the problem of its activity provokes, in the varied acts of intellect the experience of that activity’s intimate obscurity does not fail to inspire. There is for philosophy in its history a resplendence the difficult color of clarity.


[1] Herbert A. Davidson, Alfarabi, Avicenna, and Averroes, on Intellect: Their Cosmologies, Theories of the Active Intellect, and Theories of Human Intellect (Oxford: Oxford University Press, 1992), 3.

[2] Willy Theiler, quoted in Christopher Shields, “The Active Mind of De Anima iii 5,” supplement to, “Aristotle’s Psychology,” The Stanford Encyclopedia of Philosophy (Spring 2011 Edition), Edward N. Zalta (ed.), URL = <>.

[3] For the translation, and subsequent quotations, see Shields, “The Active Mind.”

[4] Gilles Deleuze, Difference and Repetition, trans. Paul Patton (New York: Columbia University Press, 1994), 114.

[5] Giorgio Agamben, Means Without End: Notes on Politics, trans. Vincenzo Binetti and Cesare Casarino (Minneapolis: University of Minnesota Press, 2000), 9.

[6] Agamben, Means Without End, 9.

[7] Daniel Heller-Roazen, Dark Tongues: The Art of Rogues and Riddlers (New York: Zone Books, 2013), 77.

[8] Heller-Roazen, Dark Tongues, 76.

About the Author:

Michael Munro is author of the open access chapbook, The Communism of Thought (Punctum Books, 2014).