Concepts of the Physical World

Concepts of the Physical World

Here is an eloquent passage from Thomas Nagel: “The understanding of the physical world has been expanded enormously with the aid of theories and explanations that use concepts not tied to the specifically human perceptual viewpoint. Our senses provide the evidence from which we start, but the detached character of this understanding is such that we could possess it even if we had none of our present senses, so long as we were rational and could understand the mathematical and formal properties of the objective conception of the physical world. We might even in a sense share an understanding of physics with other creatures to whom things appeared quite different, perceptually—so long as they too were rational and numerate…The physical world as it is supposed to be in itself contains no points of view and nothing that can appear only to a particular point of view. Whatever it contains can be apprehended by a general rational consciousness that gets its information through whichever perceptual point of view it happens to view the world from.” (The View from Nowhere, 14-15) This passage would appear to suggest a method for acquiring a thoroughly objective conception of the physical world, transcending and abstracting from the subjective perceptual perspectives with which we commonly view it. The claim isn’t that ordinary folk have access to such a conception—they are presumably stuck in the subjective conception delivered by their senses—but it is possible in principle to possess a totally objective sense-independent conception of the world that is presented to us perceptually. Thus, an absolutely objective conception (view, theory) of the physical world is obtainable by the human mind, which might coincide with that possessed by the equally objective Martian mind. This conception is characterized as mathematical, formal, and rational; anything else has been sternly bleached-out (Nagel’s phrase) as merely subjective and inessential to the understanding of the physical universe. We don’t do our physics perceptually (i.e., subjectively) but mathematically, formally, rationally (i.e., objectively). In short, physics is in principle completely objective, conceptually speaking.

I think this is wrong, seductive as it may sound.[1] There are two main problems: whether such an abstract conception of physical reality can be of physical reality, and whether the allowable conceptual materials are themselves thoroughly objective. For surely, we need more than mathematics (number theory) and rationality (logic) in order to form an adequate conception of a physical object; we need at least extension, solidity, spatial occupancy, and motion if we are to grasp what physics is about—numbers alone won’t cut it, even when combined with formal logic. You might suggest adding geometry, which Nagel does not do, but this will raise the question of our understanding of geometry—how sense-independent is it? This is too exiguous a basis on which to erect the conceptual scheme of physics, classical or contemporary.[2] The obvious gap-filler is perception, especially vision, but the senses have been excluded as subjective (rightly so). Nor will rationality serve to deliver the content of our understanding of the physical world; it is too general. So, no content has been given to the idea of an absolutely objective conception of physical reality. The empiricist view of physics has not been circumvented or undermined, and with it the inescapability of subjective physics. This means that we have no way to explain how physics manages to latch conceptually onto physical reality couched in objective terms.

Secondly, why assume that the suggested modes of thought are wholly objective? Are mathematics and logic completely free of subjective elements as we conceive them? Is there nothing of the human in our concepts here? Surely, these modes of thought carry person-related content: for example, we conceive of numbers via the digits of our hands, the symbolism we have invented, and the sortal concepts we use to count with. Not every conceivable mathematical being thinks in these ways (consider octopus mathematicians). Can we really put these completely aside and contemplate numbers purely? What about the infinite (integral to the concept of number)—mustn’t we view it from our finite standpoint? We don’t have a God’s-eye view of the infinite totality of numbers detached from any human intrusions. Logic, too, has its notations and history, its human face; and the concept of entailment is itself bound up with human conceptions of necessity (compulsion, rigidity). The way we think is the way we think, idiosyncratic as it may be. All concepts reflect the concept-forming faculty, whether innate or acquired; there are no concepts without concept-makers. Concepts have to function in the human mind and be realized in the human brain; they are not independent of our human nature. If there is a language of thought, it is a human language, not a language of angels. Our concepts are shaped by our history, evolutionary and cultural; they aren’t Platonic forms (whatever they are). So, basing physics on mathematical and logical concepts is not going to expunge subjectivity from the picture. Nor is it really necessary to expunge subjectivity in order to secure the truth and utility of physics, and even its objectivity in less demanding senses (testability, communicability, predictiveness). You don’t need to view the physical world like a god in order to have a viable and illuminating physics. Physics has always been something of a cobbled-together job—a bit of a stretch. That’s why we still don’t fully understand the physical world. It’s also why it is a real question whether we ever really talk about external physical reality—get it sharply in our conceptual sights. Many physicists have abandoned that lofty goal and settled for some sort of humanistic physics consistent with empiricism (Newton, Mach, Hertz, Poincare, the positivists, maybe Einstein, et al). In any case, the ideal of a totally objective science of physical reality is not something to take for granted, or to regard as necessary to its value, attractive as that idea may be. Physics is certainly not as subjectively idiosyncratic as, say, the culinary arts or one’s taste in sneakers. It is simply just another manifestation of our human nature (the “science-forming faculty” as Chomsky calls it). This does not detract from its impressiveness, but it does deter ambitions of omniscience.[3]

[1] See my earlier papers on subjective and objective, especially “A Paradox of Objective and Subjective”.

[2] Would anyone think that mathematics and logic could suffice to generate an adequate psychology? Surely, we also need something like introspection to give us the relevant concepts.

[3] In fact, I think we have no conception of God’s conception of the physical world; we are confined to our own conception (trivially), which is inescapably perceptual—as our conception of the mental world is inescapably introspective. Concepts don’t come to us out of thin air. (There is really a deep puzzle about where concepts come from.)