Thursday, February 5, 2009
Aristotle and Frege on thought
For reasons explained in a couple of earlier posts (here and here) the Aristotelian-Thomistic tradition regards the intellect as a distinct faculty from the senses and the imagination. The objects of the intellect are concepts, which are abstract and universal, while the senses and imagination can only ever grasp what is (at least relatively) concrete and particular. Hence your sensation or mental image of a triangle is always of a particular kind of triangle – small, isosceles, and red, for example – while the concept of a triangle grasped by your intellect applies to all triangles, whether they are small or large, isosceles, scalene, or equilateral, red, green, or black. Sensations and mental images are also subjective or private, directly knowable only to the person having them, while concepts are public and objective, equally accessible in principle to anyone. Your mental image of a triangle might be very different from mine, but when we grasp the concept of a triangle, it is one and the very same thing each of us grasps, which is why we can communicate about triangles in the first place.
Nevertheless, the A-T tradition also holds that thought is always associated with “phantasms” (very roughly, mental images). This is one reason it is easy to mistake the objects of the intellect for the objects of the imagination (as empiricists like Hume do). When you think about triangles (an operation performed by the intellect), it is natural to form a mental image of a triangle at the same time (an operation of the imagination). Even a blind person who has never seen a triangle presumably forms a mental image of the way the distinctive shape of a triangle feels, or at least of the way the word “triangle” sounds. (The formation of tactile, auditory, olfactory and gustatory images, and not just visual ones, is included in the operations of the imagination.) This is unavoidable given that (unlike angels, which are pure intellects) we are tied to the senses for all our information about the world, and arrive at general concepts only by abstraction from the data of sense as mediated by imagination. And it is one of the ways in which (as I have noted before here) there is a much tighter connection between intellect and matter on an A-T view than on a Cartesian view, even though both views regard intellect as immaterial. For A-T regards sensation and imagination as totally dependent on matter.
It seems to me that the way A-T understands the relationship between intellect and imagination might usefully be compared to Gottlob Frege’s conception of thought, as put forward in his classic essay “The Thought” (though Frege himself was no proponent of A-T). By a “thought,” Frege means what contemporary logicians call a proposition, and he distinguishes thoughts from sentences. To use a stock example, the English sentence “Snow is white” and the German sentence “Schnee ist weiss” both express one and the same thought or proposition, namely the thought or proposition that snow is white. That users of different languages can assert the same proposition using different sentences is one mark of the difference between sentences and propositions. Another mark often cited by philosophers and logicians is that a proposition remains either true or false, and thus in some sense exists, regardless of whether any sentence we might use to express it exists. The proposition that snow is white was true long before English, German, or any other natural language ever came into existence, and thus before any sentence in any of these languages ever came into existence. Furthermore, like the concepts whose abstract and immaterial character is emphasized by A-T, propositions are abstract and immaterial. The proposition that Caesar was assassinated on the Ides of March would remain true even if the entire world of concrete material objects went out of existence. Were it to go out of existence, the proposition that there are no concrete material objects would in that case be true. And so forth.
So, propositions or thoughts (in Frege’s sense of the word) are, again, abstract, immaterial and distinct from any sentence. Nevertheless, when we entertain any proposition or thought, we always at the same time entertain a sentence. As Frege famously put it: “The thought, in itself immaterial, clothes itself in the material garment of a sentence and thereby becomes comprehensible to us. We say a sentence expresses a thought.” We never “see” propositions “naked,” as it were; they never leave the house except in sentential garb. What we grasp when we grasp the thought that snow is white is not identical with the English sentence “Snow is white,” but what we grasp is nevertheless grasped through that English sentence (if we’re speakers of English, that is – German speakers grasp it instead through the sentence “Schnee ist weiss”). This, I suggest, parallels the way in which our grasp of general concepts is on the A-T view always associated with the having of phantasms, even though concepts are not identical with phantasms.
From an A-T point of view, the reason for this is, again, that we are embodied creatures dependent on material sense organs for all our knowledge. Though we are capable of moving beyond knowledge of material particulars via intellection (which is an immaterial activity), we nevertheless require phantasms (which are material) as an aid to this activity. A dog can never grasp strict universals: Rover might have a mental image of dog food, but he does not have the concept dog food, which is (unlike any possible image, which can at most apply to several instances but not all) completely general, applying to any possible instance. We can grasp universals. But (being embodied, like the dog) we tend to entertain the mental image too in the course of doing so. Similarly, while both the dog and we can hear the sentence “Snow is white” and form a mental image after the fact of how the sentence sounds or looks, only we can associate the sentence with the proposition that snow is white, which is (to simplify things a bit) essentially just what it is for us to understand language and for the dog not to understand it. But (being embodied, like the dog) we tend to form the image of the sentence in the course of entertaining the proposition it expresses.
Just as the correlation between concepts and mental images led classical empiricists mistakenly to identify them, so too does the correlation between intellectual activity and neural activity lead materialists mistakenly to identify them. But both identifications involve a category mistake, in particular a confusion of what is inherently abstract and universal with what is inherently concrete and particular.
In his book In Defense of the Soul, Ric Machuga suggests that from the A-T point of view, the relationship between body and soul is like that between words and the meaning they convey. This requires qualification, but it is a useful analogy. The difference between “bat” as applied to a stick used in baseball and “bat” as applied to a certain flying mammal has nothing at all to do with any material difference between the two word tokens. Symbols identical in their material characteristics can convey different meanings. Furthermore, the same meaning can be conveyed by symbols having very different material characteristics, as with “bachelor” and “unmarried man.” Similarly (and as I have emphasized in earlier posts) physiological processes identical in their material characteristics can be associated with different mental contents, while the same mental content can be associated with physiological processes that are different in their material characteristics.
Properly understanding the relationship between the mental and material characteristics requires, neither the postulation of an immaterial substance (as Cartesian dualists assume) nor the positing of non-physical properties inhering in a physical substance (as property dualists hold), but rather a recognition of each of Aristotle’s four causes: formal and final as well as efficient and material (the first two of which Cartesian dualists and property dualists, no less than materialists, mistakenly tend to deny). Mental content is the formal-cum-final causal aspect of a single substance and/or action of which the relevant bodily and neural processes (including sensations and mental imagery) are the efficient-cum-material causal aspect. (This is an issue I have addressed at greater length here, and in The Last Superstition.) It is only when the A-T four-causal explanatory framework is abandoned that the correlation between intellectual activity on the one hand and mental imagery and neural activity on the other comes to seem mysterious, and tempts us with false Cartesian or materialist solutions.