Physiology of Mind

Physiology of Mind

Physiology lacks a philosophy to call its own. There is no philosophy of physiology to speak of. Perhaps this is because physiology is a sub-discipline of biology and we already have a philosophy of biology. But this neglects the possibility that physiology works with concepts and theoretical constructions specific to itself, and these require philosophical treatment in their own right. Here is how the OEDdefines “physiology”: “the branch of biology concerned with the normal functions of living organisms and their parts”. As always, this definition is worth dwelling on. Physiology is the science of the functioning of living organisms and their component parts, such as the heart, the kidneys, and the brain. The word “function” here has two separate connotations: it refers to theoperationsof organisms and their parts, and it refers to the purposeof those operations. How do organisms work and why do they work that way? Thus the function (purpose) of the heart is to circulate blood, and the way this purpose is achieved is by acting as a pump with a certain structure and mode of action. Physiology must first identify the end an organ serves and then explain how that end is achieved by the organ in question. And what is an organ? The OEDhas this: “a part of an organism which is typically self-contained and has a specific vital function”. An organ is relatively autonomous in its operation and its function is specific and vital (though not necessarily a matter of life and death). So physiology is concerned with organs that have their own identity and which have a dedicated specific purpose not shared by other organs. The central concepts of physiology are therefore life, purpose, functioning,andorgan.Notice that no restriction is made to the body as opposed to the mind (this will be relevant later), nor are genetics and evolution invoked.

Venturing beyond the dictionary definition, we can make a number of other observations about physiology (the science and the reality). First, there is a division of labor among organs: some do one job and some do another (nineteenth century physiologists compared the body to a factory). Second, function and structure are intimately connected: whatever the function of an organ is, it must have a structure that suits it to perform that function; and physiology as a science must characterize this relation. We may think of it as a fittingrelation: it resembles the way artifacts fit their function—they must be physically capable of performing it. Thus physiology (functioning, activity) must dovetail with anatomy (structure, architecture). Third, although organs are sharply differentiated, they must be integrated—because they have to work harmoniously together. Rogue organs do nobody any good. They need some sort of central command or supervision (here is where the brain comes in handy). Fourth, and connected, organs belong to organ systems, forming complex organs—consider all the organs that go into digestive systems. These must be integrated together, but they also need to be integrated with other organ systems. Accordingly, there is a hierarchical structure to physiology: systems, subsystems, individual organs, components of such organs, etc. Fifth, there is a normative aspect to physiology: that is, we have the notions of health and disease, normality and pathology. This is because of the teleological element: organs are healthy or defective according as they achieve their purpose, which is to preserve life (which we assume is a good thing). Sixth, just as the organism exists in an external environment which it must negotiate, so the several organs of the body exist in an internal environment; and in both cases adjustment and accommodation are required. Here is where homeostasis comes in—the need to keep the internal environment stable and contained within certain limits (temperature being the most obvious parameter). The organism exists in a physical environment and one that contains other organisms; the organs exist in a chemical environment and one that contains other organs. There is a nesting of environments. The organism has a certain Umwelt, but so does the individual organ. This point gives rise to the seventh observation: organs, like organisms, are input-output devices. Something goes in and something comes out. Often the organs function as a conversion device—as with the lungs and stomach. All organs need nutrients to be absorbed in order for actions and processes to be powered. The components of the body are not isolated and cut off. Thus the organs need to contain interactive mechanisms—devices that make things happen, often of elaborate design. The system is intricate and interlocked, though differentiated and distinct. Eighth, the organs have a genetic basis, a distinctive embryogenesis, and an evolutionary history; they are certainly not “acquired” by means of interaction with the environment. The tabula rasais a very bad model for physiology. The heart is as hard-wired and pre-determined as any nativist could wish. Ninth, despite the manifest variety of organs, there are certain physiological universals, particularly pertaining to cellular structure: all organs are made of cells, though the cells typically differ histologically. Thus macro-physiology is highly heterogeneous, while micro-physiology is quite homogeneous (the cell with its nucleus, membrane, and mitochondria). As it were, the atoms are alike, but the objects they compose exhibit considerable variety, according to their specific jobs. Tenth, we can, for any organism, make a list of its characteristic organ systems, which serve to fix its phenotype; these may overlap with other species or may be unique to the species in question. By my reckoning, human physiology contains the following organ systems: digestive, respiratory, sexual, circulatory, immune, motor, postural, sensory, protective, and mental (with many subdivisions: see below). So the magic number is 10—other species may well have less, though in general this number seems to apply to all but the simplest organisms. Thus evolution needed to produce 10 organ types that work together to keep an organism alive. Subtract any of them and you tend to get a dead organism. Physics and chemistry have their types of particle; physiology has its types of organ. The raison d’etreof each is its contribution to maintaining life.

Before I turn to applying this conception to the mind, it will help to talk in some detail about specific organs, so that we have a concrete point of comparison. The heart is composed of two types of cell, known as cardiomyocytes and pacemaker cells, which have different functions. The former enable muscular contraction and are cylindrical in shape. They have high mitochondrial density that enables them to produce large amounts of ATP, which makes the heart resistant to fatigue. Heartbeats are caused by the shortening and lengthening of fibers. The gross anatomy of the heart divides it into the atria and the ventricles, chambers that receive blood and pump it out, respectively. The tissue of the heart is a type of muscle tissue. By pumping blood the heart serves its purpose of circulating blood throughout the body to maintain organs and perform other functions. The functioning of the heart is closely linked to the respiratory system. The kidneys, for their part, have a different shape (more like a large bean) and are made up of different cell types called nephrons. They process liquids and expel urine. The liver is a large organ that contains hepatocytes and endothelial cells, boasts two lobes, is adjoined to the gallbladder, and performs a variety of functions related to digestion, also secreting bile. Diagrams of these organs can be made and they have a distinctive macro anatomy and microanatomy. Structure is suited to function; function is specific; there is input and output; there are links to other organs. This is the stuff of physiology as defined above. It goes beyond more general biological concepts, such as genotype and phenotype, natural selection, species, evolution, reproduction, and so on. Physiology is primarily concerned with the concept of an organ, understood in the way outlined—structure, role, purpose, operation. As remarked, this concept is not conceptually tied to the body or to the concept of the physical: it could have turned out that organisms house non-corporeal organs (as was supposed for the elan vital), so long as these entities fulfill the general abstract definition of an organ. If cavities in the body perform a role analogous to meaty tissue, then they too would count as organs, since they aid life. Or a Cartesian biologist might postulate an immaterial organ responsible for circulating the blood, on the (mistaken) assumption that such an impressive and important feat could not be performed by mere matter and needs the help of the ethereal. Most significantly for our purposes, nothing in the definition of physiology requires that the mindnot count as an organ possessed by an organism. Hence we have the idea of a physiology of mind—a science of mental organs.[1]That is, psychology is a branch of physiology. Not just a branch of biology, but a branch of the branch of biology called physiology. Nor is this conception in any way precluded by the etymology of the word “physiology”, since this word derives from a Greek word meaning simply “nature”. Nothing specifically physicalis entailed (whatever exactly “physical” is supposed to mean).[2]

The basic idea is far from novel (Chomsky has been speaking of “mental organs” for decades and comparing them to bodily organs). What I want to do is apply the conception developed above in an explicit theoretical way, so that the mind emerges as fully and properly physiological–not metaphorically but literally. The mind really is an aspect of the physiological constitution of the organism, animal or human. It is literally a collection of physiological organs. Recall the dictionary definition of “physiology”: “the branch of biology concerned with the normal function of living organisms and their parts”. Surely it is obvious that the mind of an organism is part of its normal function: the mind has a function and this function is normal. Or rather, the mind is made up of faculties (“organs”) that have a function and which function in the life of the organism. The sense experiences of bats, say, have a function and they function in the life of a bat—they have a purpose, a nature, and a mode of operation. We refer to the senses as sense organsfor a reason—they literally are organs. But they are not purely bodily organs—they are psychophysical organs; they have both a mental and physical aspect. Their having the former aspect in no way disqualifies them for the title “organ”. Not that it matters whether the word “organ” fits as a matter of common usage; from a theoretical point of view, vision (say) is as much a vital biological property of an organism as the stomach. There is no principled or interesting dividing line here. Animals have organs in their bodies and they have organs in their minds (or partly so). Again, the dictionary definition of “organ” confirms this topic-neutrality: an organ is just part of an organism that is “self-contained and has a specific vital function”. It would be pointless to quibble over the word “part” here on the grounds that mental faculties are not really partsof an organism; we could easily rephrase the definition by using “aspect” or “property” or “trait”. The interesting question is to what extent mental organs share the characteristics I attributed to organs in general, for that is what determines whether the concept of the physiological is apt. So: is the mind organ-like?

Consider the language faculty. There is much controversy on this subject but I propose to cut through all that and adopt a specific perspective, roughly that developed by Chomsky. I will accordingly say that language is an internal system (with an external expression) that consists of rules of computation and a lexicon of word-like elements. A grammar specifies the structure of this system and takes a generative form. The grammar is innate and modular. Sentence structure can be represented by tree diagrams. The grammar outputs infinitely many possible strings on a finite basis. The internal system connects to sensory systems (typically hearing) and to motor systems (typically speech mechanisms), as well as to cognitive processes such as logical reasoning. Given this general conception, it seems evident that the language faculty counts as an organ and hence as an element of human physiology. It has a complex internal structure, relatively specific, with connections to other mental organs, an innate basis, and even its own mode of depiction (those tree diagrams). If we ask what its function is in the life of the organism, the answer is not far to seek: it serves either as an aid to thought or as a means of communication (depending on your view of the purpose of human language). In either case (or in both) language performs a vital biological function in the life of the human organism; you are at a comparative disadvantage without it. It contributes to reproductive fitness. It propagates the genes. It is also an input-output system: sensory inputs, including speech, and motor outputs, also vocal (sometimes gestural). You report what you see and hear and you talk about what you think and feel. So it is connected to other organs or modules or faculties, and hence operates in its own specific internal environment (consider internal speech). It is differentiated yet integrated, self-contained yet embedded. Thus it counts as part of human physiology—our nature as living things, our phenotypic identity. Essentially, it has a certain functional architecture that fits into the life of a particular species—a compositional structure and characteristic mode of operation. As plants engage in photosynthesis as part of their mode of living, so humans engage in linguistic synthesis as part of their mode of living: they put sentences together by following certain procedures and this product aids them in life. And this faculty can exhibit signs of ill health and disease if it fails in its purpose, as other organs can: thus aphasia and the various types of language pathology. The language faculty is not supposedto issue in nonsense or grammatical error, yet it sometimes does—it is then not working according to its function. There is right and wrong, good and bad, well-formed and ill-formed. Physiology is inherently vulnerable to breakdown and malfunction, and language is no different. This is a logical consequence of having a biological purpose.

Much the same can be said about other commonsense mental categories: perception obviously, but also memory and reasoning. I won’t discuss these in detail; it is fairly easy to see how the story will go. There will be a specification of the organ’s function and a description of its enabling structure–the former obvious, the latter less so. Then we will need to locate it in a wider system, characterizing its inputs and outputs, and its internal environment. There will be specific architectural details, as well as some shared properties (constituent structure looks like a universal). We might be able to draw a map of the mind relating its various components—a full mental anatomy.[3]No doubt there will exist a physical and chemical basis to the mental organs at a deeper level of analysis (which will not replace the higher levels), and a cellular substrate. The important point is that we are not now engaged on a completely different enterprise from that of traditional physiology; we are merely extending that enterprise. The same theoretical framework is employed, but now applied to the physiology of mind.[4]A stubborn residual dualism will be resisted in favor of a more unified vision of the organism. The mind will be granted a lot more internal structure than on certain traditional conceptions, which insist on a radical discontinuity between the study of the body and the study of the mind (the body jammed with structure, the mind merely a blank nothingness). The body turned out to have a lot more internal structure than early physiological inquirers suspected; the mind will likely reveal a lot more structure than similarly benighted theorists assume (and has already done so). Framing the questions in physiological terms provides an apparatus for inquiry that encourages the same kind of open-minded exploration. Approaching an alien species, we would expect to discover its internal bodily organization—its organs and their processes—but we should adopt the same attitude towards its mental organization. The most basic principle of physiology, whether of the body or the mind, is that nature has made organisms to consist of differentiated but integrated organs serving specific functions. There is no such thing as blank and homogeneous physiology.[5]

[1]Kant speaks of the “physiology of understanding” in relation to Locke’s project in the Essay: this was a good insight on his part. See the preface to Critique of Pure Reason.

[2]The physiological conception I am advocating is not to be confused with the perspective of so-called neuroscience. There is nothing reductionist about my proposal and its preferred descriptive vocabulary is not the same as that of the brain sciences. That vocabulary is geared to the type of cell composing the brain (neurons) as well as the gross anatomy of the brain. By contrast, the vocabulary of physiology abstracts from this detail and talks of organs, function, structure, life, and organic systems. This talk is topic-neutral and in no way presupposes a “physicalist” view of the mind (whatever that might be).

[3]It is an interesting question whether consciousness counts as an organ in its own right or whether it is a quality possessed by various mental organs. I suspect the latter to be true, but in either case it would be a physiological phenomenon, perhaps analogous to the smoothness of bodily organs, which is shared by many such organs.

[4]Let me put in a word for the “second brain”, that neural structure in the gut that regulates digestion. Assuming that there are mental correlates to its operations, we could postulate a “second mind” that harbors its own set of mental organs (see my “The Second Mind”, in Philosophical Provocations, 2017). I suspect many people will be more ready to grant physiological status to this lowly mind than to the more familiar mind that engages in logical reasoning and artistic creativity. But really the “head mind” is no less organic than the “gut mind”.

[5]Even a physiology of an immaterial Cartesian substance, if such there could be, would deal in organs and their activities, since the mind is made of a number of interacting faculties that need an operational structure. The immaterial mind would not be a formless nothing any more than the body is. Perception, thinking, language, memory, emotion, and volition will all require specific configurations of the immaterial stuff in which the mind is held to reside. And there will be the same questions about purpose, mode of operation, etc.