§12. Nihil est in Intellectu...

Aristotle’s theory of sense perception eventually became almost every philosopher’s theory, even those we do not think of as Aristotelian, like Hobbes and Locke. The first postclassical philosopher to take a stand against Aristotle’s theory was William Ockham, the first “anti-representationalist” in the theory of knowledge (§32).

Before Aristotle, Greek philosophers discussed cognitive functions without reference to the soul. In the early fifth century Empedocles explained details of vision, hearing, and cognition without referring to psuche as the place where they happen or whose power they express. He thought they happen in the heart and express the heart’s power. By the end of the century, however, the new idea is to unify sensation, passion, memory, and thought in a comprehensive psychology, which requires a comprehensive psyche. Democritus depicts the soul as the central organ, composed of the finest, fastest atoms. Life, emotion, and cognition are expressions and powers of this psuche organ. The medical authors also contribute. A Hippocratic author writes, “The soul... divides her attention among many things... to hearing, to sight, to touch, to walking, and to acts of the whole body... the soul when awake has cognizance of all things—sees what is visible, hears what is au­dible, walks, touches, feels pain, ponders.”¹⁰²

Aristotle does not assume body and soul are separate entities, as Plato had, influenced by Pythagorean thought. Body and soul are related as the matter and form of one organic substance. Soul is the form or functional organi­zation of an organism’s matter. As soul enlivens matter, makes a body alive, organized, an organism, it is only logical to endow every organism with soul.

We expect a mechanical change. Interaction between reflected light and the eye is a mechanical exchange—light energy, nerve energy, the activa­tion of the whole complicated mechanism of the eye. That is not the change Aristotle has in mind. Nothing propagates from the object to the eyes. The transparent medium takes on the form of the object immediately and conveys it immediately to the eye. Touch by the impression of the visual ob­ject changes the eye from its first actuality—it is able to see red—to its second actuality—it sees red. In this change the eye acquires no new attribute; in­stead, a power it had always possessed is momentarily activated.¹⁰³

He describes the change from first to second actuality as an energeia rather than a kinesis. It is always complete; there is no process. As soon as vision begins, it is true that I see. The alteration that perception works in the eye is not a change in form, mechanically changing the eye from one condition to another. Instead, it actualizes a specific corporeal potency for form. Look at the flowering tree! When you do, the eye actually has a form (a color) that it only could have had the moment before.

This account seems to inaugurate the European preoccupation with “rep­resentation.” The challenge is to make the being of the thing present again in the intellect. Aristotle says that “generally, about all perception we can say that a sense is what has the power of receiving into itself the sensible forms of things without the matter, in the way in which a piece of wax takes on the impress of a signet-ring without the iron or gold.” Sight is the potential to be changed by color; hearing, potentially changed by sound, and so on. Only a body can be changed in this way, which is why perception occurs in the organ. It supplies the matter that undergoes change (from first to second ac­tuality), caused by the sensible form.¹⁰⁴

Aristotle explains aisthesis as “a kind of being moved upon and acted upon.” Like Plato he emphasizes passivity. Aisthesis is an impression, a pas­sion, something the body is compelled to receive by a dominant power, not unlike the condition of a slave. What we perceive are not substances but qual­ities. Aristotle divides these qualities into those peculiar to one sense and others common to all, the so- called common sensibles: motion, rest, number, figure, and size. We can see motion, feel motion, hear motion, perhaps even smell it (aroma intensifying with proximity). Each sense is unerring with re­spect to its special object. “It never errs in reporting that what is before it is color or sound (though it may err as to what it is that is colored or where it is, or what it is that is sounding or where that is),” an inerrancy attributed to the passivity of the organ.

Sensible, qualitative form is instantaneously and non-mechanically trans­mitted in the medium from the object to the organ, where perception occurs. We see in our eyes, our eyes see as our fingers touch. Typically, multiple sen­sory organs are simultaneously active, though the result is not disordered powers oblivious of each other. Any animal (perception distinguishes an­imal from plant) responds to perception in an organized way, which requires a center where all the perceptual chains terminate. Aristotle locates this central soul faculty—the so-called common sense (koine aisthesis, sensus communis)—in the heart. The eyes see white, the tongue tastes sweet, and the heart synthesizes the mix into an ensemble, a sweetness that is white, or a white that is sweet. Combining things so different—as different as color and taste—is work Aristotle assigns to imagination (phantasia). Imagination combines sensible forms to create images. He explains that “images (phan- tasmata) are like sensations (aisthemata) but without matter.” These images image the form of the things that have their qualities. The synthetic power of imagination—the power to image the object, imagine the unity, intuitively combining many sensible forms in one substance—is at once the beginning of science and the mother of all error.¹⁰⁶

Imagination is a versatile power. It is synthetic, for example, putting color, heat, and motion in the same (imaginary) body. It is retentive, retaining and combining sensible traces. It even has an intelligent capacity to interpret per­ceptual traces as signs of possible or actual realities.

Thinking is different from perception but does not occur without im­agination, which does not occur without perception. “To the thinking soul phantasms serve as if they were the contents of perception,” Aristotle said. “That is why the soul never thinks without a phantasm.” No thought without an image—an idea with long legs. Hobbes liked it, Gassendi and Locke liked it, even Leibniz liked it: “The senses provide us with materials for reflections: we could not think even about thought if we did not think about something else, i.e., about the particular facts which the senses provide.” What recommended this idea to Aristotle? Few things are radically sepa­rate from the sensible qualities of nature, which was a difference from Plato. Objects of thought are not immaterial ideas; they are corporeal changes and require a sensible vehicle. We cannot count without changes, and we cannot think without changes, which are our phantasms.¹⁰⁸

Aristotle supposedly expressed what became a motto of empiricism, usu­ally cited in Latin: Nihil est in intellectu quod non prius furit in sensu. There is nothing in the intellect that is not first given in sense. Gassendi remembers this when he writes of that “celebrated saying, There is nothing in the intellect which is not first in sense... the intellect, or mind, is a tabula rasa, on which nothing has been engraved or depicted.” Locke remembers it when he writes, “There appear not to be any ideas in the mind before the senses have con­veyed any in.” Leibniz quotes Locke’s words, adding the Latin phrase himself in the New Essays.

There is no scientific knowledge without perception, but no perception is in itself scientific knowledge. “Scientific knowledge is not possible through the act of perception.” Aristotle explains why.

That which is commensurably universal and true in all cases one cannot perceive, since it is not a this and it is not a now; if it were, it would not be commensurably universal—the term we apply to what is always and eve­rywhere. Seeing, therefore, that demonstrations are commensurably uni­versal and universals are imperceptible, we clearly cannot obtain scientific knowledge by the act of perception... for perception must be of a partic­ular, whereas scientific knowledge involves recognition of the commensu­rably universal.¹¹⁰

Aristotle rules out scientific knowledge from perception alone, as if just looking might yield scientific knowledge. Perception is a moment in the gen­esis of knowledge, a phase in a greater whole. We cannot think without a form on which to think, and the way forms get to the intellect is by percep­tion. Without the senses we have no data, but in thinking we exercise powers distinctive of the rational soul to combine and abstract qualities of the sen­sory form and extract an intellectual, intelligible, noumenal form that is the essence and truth of nature.

The substances of nature, the objects of scientific knowledge, are always more and different than is given to perception. Their truth lies in their es­sence and this essence cannot be perceived. The word “essence” comes from Latin esse, “to be.” The essence of a thing is its very being, that about it which most veritably is or is in being. This essence is the norm of veridical percep­tion and the ultimate Aristotelian cause (formal cause) of nature’s intelligi­bility. Aristotle implicitly accepts Plato’s argument in Theaetetus. Perception cannot think. What scientific knowledge has to think on is imperceptible, even though we require perception to attain this imperceptible.

Sensible and substantial or intellectual form are not different entities. Form is form, and intrinsically intelligible. A form is called sensible because it arises in the soul with sense perception. That same form is intellectual for an animal possessing an intellect. Furthermore this intellect cannot be ma­terial; it has to be incorporeal because while sense acquires sensible forms, nous acquires forms simpliciter. The intellect “must then, since it thinks all things, be unmixed... in order that it may know; for the intrusion of any­thing foreign hinders and obstructs it.” Perceiving red is becoming red and as such is a bodily change. But anything is a logical object for intellect, and the forms it receives are essences. These two features are difficult to attribute to a corporeal change, despite the fact that thinking is impossible without a sensory image.¹¹¹