Home Economics Aquinas’s theory of perception: an analytic reconstruction
Intellectus Agens as an Efficient Cause
The abstractive function of the intellectus agens has always been a difficult bit of philosophy-of-mind theory to elucidate adequately. In the famous metaphor of the ‘army in retreat’ found in Chapter 19 of Book II of the Posterior Analytics, Aristotle suggests that out of sense comes memory, and out of memory then comes experience. ‘Sense’ here possibly refers to an awareness of an individual, ‘memory’ to the stored awareness of many such individuals, and ‘experience’ to the formation of the species intelligibilis by the intellectus agens. In his Commentary on the Posterior Analytics, Aquinas uses the same example. He elaborates by writing that the ‘nature of mind’ is such that it ‘can also cause this in virtue of the intellectus agens, which makes things intelligible in act by abstraction of universals from singulars’ (bk II, lect. 20).
Just as Phantasm-2 is a conditioning of the mental act of awareness enabling the perceiver to be aware of the incidental object of sense, the sense memory stores these structured mental acts of awareness. On this suggestion, then, possibly the intellectus agens is possibly a higher-level structure, which works through the stored structures of the sense memory. In this way, the intellectus agens is able to focus attention on the individual as a member of a natural kind and not as a bundle of sensations. The intellec- tus agens, it would appear, is the enabling structure permitting the individual knower to abstract the essence or sortal properties from the set of individuals forming the class determined by the natural kind. The vis cogitativa has prepared the ground for the process of abstraction. The vis cogitativa renders the bundle of sensations perceivable as an individual of a natural kind; in a similar manner, the intellectus agens renders the essential properties structuring the natural kind in the individual primary substance intelligible for the intellectuspossibilis. Every potency requires an entity in act in order for the particular potency to be rendered into an actual state. The vis cogitativa and the intellectus agens serve as entities always in act ‘searching’ for potentialities
(Phantasms-1 and Phantasms-2) to become a qualitatively different state of actuality—a perception of an individual of a natural kind or a concept of the essence ready to be known by the intellectus possibilis.
To put the matter somewhat differently, it might be fruitful to look upon the functioning of the intellectus agens in a manner analogous to the conditioned awareness of the vis cogitativa. The intellectus agens utilizes a structured awareness in interpreting collections of individuals in what constitutes them as belonging to a natural kind or having essential natures. As the vis cogitativa in utilizing Phantasm-2 contributes towards an awareness of an individual, so too the intellectus agens contributes towards an awareness of the essential, sortal properties, which constitute a nature or essence. These essential natures are abstracted as intelligible species; in Aquinas’s philosophical language, this happens by a scanning of the phantasms through the intellectus agens and then by this intentional result or form being implanted in the intellectus possibilis, which is the cognitive faculty where these essential natures are known. The implication of this narrative is that the essential properties are known by a conditioned awareness— the scanning—of Phantasms-3, in that Phantasms-3 are the residues of perceived individuals, which are Phantasms-2. The notion of ‘making a nature’ is the most fruitful way to interpret the abstractive function of the intellectus agens; Geach discussed this dimension rooted in Aquinas’s texts:
We can now say something that goes for all concepts without exception: Having a concept never means being able to recognize some feature we have found in direct experience; the mind makes concepts, and this concept-formation and the subsequent use of the concepts formed never is a mere recognition or finding but this does not in the least prevent us from applying concepts in our sense-experience and knowing sometimes that we apply them rightly. In all cases it is a matter of fitting a concept to my experience, not of picking out the feature I am interested in from among other features given simultaneously.
Geach refers to the intellectus agens as ‘the mind’s concept-forming power.’ One must be careful in considering his analysis of the intellectus agens. This intellectual power renders the conditions appropriate by means of an intelligible species—a species impressa—so that the intellectus possibilis can possess a concept to be understood, which would be the species expressa. As South keeps reminding readers of Aquinas on mind, the intellectus agens does not ‘know’ a concept. On the contrary it renders a concept possible through its formation of a species intelligibilis by means of its abstractive ability. Aquinas writes about this function in the following passages: ‘Similarly, we understand the light of the intellectus agens, in so far as it is the reason for the intelligible species, making them actually intelligible’ (De Veritate II, q. 10 a. 8), and ‘the intellectus possibilis [. . .] is brought to completion [i.e. it actually understands] only through the acquired intelligible species, which are abstracted from the senses’ (q. 10 a. 8). In his De Veritate, Aquinas writes: ‘The active intellect is described as that whose function it is to make all things, and the possible intellect as that whose function it is to be made all things’ (De Veritate I, q. 2).
In De Veritate, Aquinas explicitly refers to the intellectus agens as ‘making’ the concepts for the intellectuspossibilis; this is how a human knower, to borrow from Kenny, ‘acquires complicated concepts from experience’:
Physical light is seen through itself only in so far as it is the reason for the visibility of visible things and a kind of form making them actually visible. Now, we see the light, which exists in the sun only through its likeness, which exists in our sight. For as the specific nature of stone is not in the eye, but its likeness, so the form of light, which is in the sun cannot be the same form that is in the eye. Similarly, we understand the light of the intellectus agens, in so far as it is the reason for the intelligible species, making them actually intelligible. (De Veritate II, q. 10 a. 8)
Martin’s suggestions are in line with the general thrust of the interpretation of the structure and function of the intellectus agens put forward in the final sections of this chapter. The intellectus agens, in the manner of an efficient cause, actually makes the species intelligiblis, which is a necessary condition for the formation of a concept that in turn is known by the intellectus possibilis. This is a far cry from the sense of abstraction often found in scholastic accounts of the intellectus agens in Thomas, where what this faculty does is ‘pick out’ essential features in the phantasms. This is the interpretation of the intellectus agens that concerned Geach in Mental Acts. To ‘pick out’ renders incomprehensible Aquinas’s discussion of the intellectus agens as an efficient cause. The function of the intellectus agens is to provide a ‘structured’ awareness of the Phantasms-3 stored in the vis memorativa. Hence, what Aquinas’s philosophy of mind consists of is a level of structured mental acts. The structured mental act of the vis cogitativa is aware of an individual as a member of a natural kind. This structured awareness is accomplished through the means of Phantasm-2. The remnant or residue of these acts of awareness is stored in the vis memorativa as Phantasms-3. These are remnants of structured awarenesses. The intellectus agens then is a higher-level structure that ‘makes’ or ‘interprets’ the essential properties common to the natural kind found potentially in the collection of a kind of individuals stored as Phantasms-3. As the vis cogitativa is always ‘working, as it were, finding individuals of natural kinds, so too is the intellectus agens always ‘working’ trying to put a set of essential or sortal properties into the natural kind found potentially in the individual primary substances represented as individuals by Phantasms-3. What the intellectus agens makes is then placed in the intellectus possibilis, as a conceptus with esse intentionale. This concept is the means by which human knowers understand the nature of the external world. This is the final part of the epistemological realism in Thomas that is aligned with his ontological realism. The ontological realism is determined by natural kinds that are in turn determined by sets of synthetic necessary sortal properties. This is the structure of the forma substantialis that determines the foundation for the essential properties. The intellectus agens, as an efficient cause, makes a concept, which in principle is that by means of which a knower is able to know the fundamental ontological categories that determined the structure of the external world. Of course, this ontological structure is rooted in individual primary substances, which are individual instances of natural kinds.
In De Veritate, Aquinas suggests that the intellectus agens is intrinsically active and always ready to make a species intelligibilis from the phantasms in the internal sensorium:
In every act by which human knowers understand, the action of the intellectus agens and that of the intellectus possibilis concur. Moreover, the intellectus agens does not receive anything from the outside. Only the intellectus possibilis does so. Hence, with reference to the requirements for human thought and human thinking, there is nothing on the part of the intellectus agens to keep human knowers from always understanding. However, the same does not hold for the intellectus possibilis, because it is brought to completion—i.e. it actually understands— only through the acquired intelligible species, which are abstracted from the senses. (De Veritate II, q. 10 a. 8)
On this interpretation, Geach’s account on abstractionism in Mental Acts is illustrative. The ‘content’ material for the interpretive function of the intellectus agens is Phantasm-3. Phantasms-1 provide the material content from which the conditioned awareness of the vis cogitativa was produced. Likewise, Phantasms-3 provide the content from which the structured awareness of the intellectus agens is produced. The role assigned in this analysis to Phantasm-3 in concept formation by means of the species intelligibilis is expressed in the Posterior Analytics, where Aristotle explicitly affirms the important function of memory in the process of the ‘making of the universal’.
The notion of the intellectus agens is, of course, in dire need of a thorough conceptual analysis for analytic historians of philosophy. However, the suggestion at the end of this study of phantasms is the following: structured mental acts ‘perceiving’ on the level of the vis cogitativa, ‘storing’ on the level of the vis memorativa, and ‘abstracting’ on the level of the intellectus agens all enable the human knower to be aware of the richly diversified ontology of individuals grouped in natural kinds that make up the world Thomas Aquinas assumed to be the case. This is how Thomas offers a cognitive explanation of how all of this is possible in his theory of an Aristotelian philosophy of mind. The above sketch of levels of structured mental acts might prove fruitful towards providing a thorough elucidation of such an unwieldy concept as the intellectus agens.
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