Reductionism

Lecture 19.  October 28 and 29.

Afterthoughts.   In order to make a place for psychology at the table of science, psychology’s founder, Wilhelm Wundt, proclaimed an “alliance” between philosophical psychology and physiology, fulfilling an unbroken tradition reaching back to ancient Greece.  Claimed as an ally, physiology at the same time posed a danger to psychology, threatening its autonomy as a science by reducing mental concepts to neural facts and its existence as a discipline by revealing its subject matter—the soul, or its replacement, consciousness—to be an illusion.  Redefining psychology as the science of behavior dispensed with the ghost in the machine, but only postponed psychology’s reckoning with physiology.  While the biological substrates of behavior eluded early neuroscience, they had to be there and would one day be discovered. 

The aim and concepts of reductionism were developed by philosophers in the positivist tradition that founded philosophy of science as a discipline.  The early positivists, led by August Comte, suggested that sciences could be arranged in a historical and philosophical hierarchy reflecting their relative appearances in time and their relative philosophical statuses from last developing and least basic science (sociology) to first developing and most basic science (physics).  The idea was, very roughly (details were worked out later), that the laws of group behavior (sociology) would reduce to the more basic laws governing the behavior of humans comprising social groups (psychology), whose laws in turn would reduce to the more basic laws of biochemistry governing the nervous system of each person (neuroscience), which would reduce to the laws of chemistry, and thence to the laws of the particles making up each chemical element (physics).

The problem of reduction arises when a domain is addressed by two theories, raising the question of how such theories might relate to one another.  Historical examples include theories concerning the movements of the planets, heat, and the behavior of gases.

One possibility, of course, is replacement: One theory is correct and the other is wrong, and the first, typically newer, theory replaces the other.  A paradigm instance is the replacement of the Ptolomaic, earth-centered, account of the solar system by the Copernican, sun-centered, one.  In this case the conceptual furniture of the universe was left unchanged: Moon and Mars, Jupiter and Sol remained, but their positions and motions were understood and explained in new ways.  In other instances, replacement entails the complete elimination of things posited by older theories.  For example, as atomic understanding of matter and energy progressed in the 18th century, older concepts used to explain phenomena such as heat were found to be without reference: Elimination was the fate of phlogiston and caloric and of fluidic theories of heat and electromagnetism in general.

The second possibility is reduction:  A theory might turn out to be valid at one level of description and explanation, but reducible to a more basic and more general theory.  A paradigm instance is the relation between the classical gas laws and the atomic theory of matter.  Early physicists had shown that the behavior of gases could be predicted and explained by laws using the variables pressure, temperature, and volume.  So, for example, pressure cookers maintain a gas (steam) at a constant volume so that as the air and water vapor is heated the temperature in the cooker rises; on the other hand, heating air causes a hot-air balloon’s bladder to expand.  The gas laws were mathematically precise and descriptively true.  As the atomic theory of matter developed, however, heat came to be understood as the rapidity of molecular movement in a physical body: the more rapid the motion, the higher the temperature.  Applied to gases, atomic theory explained why the gas laws were true.  In the pressure cooker, the atoms of water vapor trapped inside move faster and faster as heat is applied, and so temperature rises; in the hot-air balloon, the molecules of heated air push against the enclosing bladder, forcing it to open more, and volume increases. 

In a reduction, the reduced theory is retained in science, but is explained at a lower level of discourse (atoms rather than gasses) and is incorporated into a broader, more general, account of nature (gasses are seen to follow the same principles and are made of the same stuff as all matter without exception).  This example shows that when psychologists discuss and fear “reductionism,” they usually are discussing and fearing replacement instead.  Note, also, that replaced theories, even though known to be false, may be retained for practical use.  Calculating one’s location on the earth under Ptolomaic assumptions is much easier than under Copernican ones, and for centuries after Copernicus’ Revolution of the heavenly orbs sailors sailed the seas of a notionally earth-centered universe.

Forethoughts.  Early psychologists flirted with reductionism, but most moved away from it.  Wundt’s alliance with physiology weakened during his career.  In his early writings, he often proposed physiological accounts of mental processes such as attention, but in the end the alliance became more a matter of experimental method than of theoretical substance.  Freud was besotted with the prospect of reduction in his “Project for a scientific psychology,” but never published it, although its ghostly echoes remain in his later so-called “pure psychology.”  Behaviorists were similarly ambivalent in their relationships with physiology.  John Watson, who launced the behaviorist movement, was a materialist and sometimes talked like a reductionist and eliminativist, but it was more bluster and attitude than a real attempt to do psychology as physiology.  His student Karl Lashley, did try to carry out a reductionist program with respect to learning, but it never came to anything, probably because the research tools needed lay decades in the future.

In the later 20th century, cognitive psychologists and allied philosophers of mind declared their independence from physiology and denied that cognitive theories could be reduced to or eliminated by neuroscience.  Their most formidable argument derived from the symbol-system version of cognitive psychology, and is known as the argument from multiple realizability.  In brief, the argument is this.  In the symbol system view, cognitive processes consist in the manipulation of symbols by logical rules.  Symbol manipulation can be performed equally well by different physical devices, most notably organic brains made of tissue and electronic brains made of silicon and metal; hence, the familiar metaphor that the mind is like a computer, or, more precisely, that mind is to brain as program is to computer.  Cognitive theorizing, whether in psychology or artificial intelligence, was about formally defined symbols and rules; how symbols and rules were grounded in a brain or a computer was “mere implementation.”  At the margin, this meant that a person’s mind could, in principle, be written as a computer program and downloaded into a computer, with no resulting change in behavior. 

Important to the argument was the distinction between types and tokens.  Each person is a token of the (conceptual) type “human being;” each dime in your pocket is a token of the type “dime.”  The beauty of multiple realizability—known in philosophy as non-reductive physicalism—was that it was materialist—no soul-stuff need be invoked—yet it preserved the theoretical autonomy of psychology.  Every mental event, or token (in the sense of a piece of cognitive computation), corresponded to some physiological or electronic token, but no mental type shared across cognizers, organic or inorganic (e.g., knowing that a dime is a unit of US currency) corresponded to any physical type in the system implementing a cognitive system.  The idea is perhaps clearest in the case of computer programs.  One can play a game such as Command and ConquerÔ on a PC, an Xbox, or a Mac, and it will look and feel the same even though the underlying machine code is different in each device.  Reduction is therefore only trivially true and poses no threat to psychology.  Brains and machines carry out computations, but no theoretical gain is won by worrying about how they do so.  Description, prediction, and control, the scientific goals of theorizing, can be fully met at the cognitive level.

Nevertheless, reductionist and eliminativist proposals have been revived in the 21st century, as neuroscience has made enormous advances in understanding the physiological mechanics of mental processes. Clinical psychologists are struggling to survive in the age of Prozac.  Even economics, which would seem immune to reductionism because it deals with social entities such as money and interest rates, has within it a new approach called neuroeconomics.

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Universal and Particular: Implications for Social Science

Lecture 15.  October 9 and 15.

Afterthoughts.  Essential to the Enlightenment Project was (is) the universal claim of reason found in Condorcet’s Sketch, in which he looks forward to the day when all men everywhere will be governed only by their own reason, when particular religions and cultures will have given way to a universal, rational, way of life.  Thinkers of the Counter-Enlightenment, such as Herder, on the other hand, defend the particularities of culture and language against the universal empire of reason.

While it looks like this is fundamentally a disagreement about values and human nature, it has important implications for conceiving of psychology and the other social sciences as sciences.  The possibility and practice of natural science rests upon the idea that the laws of nature are universally the same everywhere and everywhen, as in Newton’s law of universal gravity: This is the View from Nowhere I discussed in our first week.  If the Enlightenment’s claim of universal reason is correct, then psychology and the other social sciences can be sciences in the same sense as physics.

Consider one path to such a conception of psychology as science, the one taken today by mainstream cognitive science, the symbol system concept of mind.  If people are to be universally governed by reason, then one has to have an idea about what reason is.  We have met one candidate for defining reason, in the Classical period with Plato and the Stoics.  Plato modeled rationality on geometry, and the Stoics developed the idea of mind as logic (logos) in their propositional calculus.  Key to both views is separating reason as a universal process from the particular things reasoned about.  The Pythagorean theorem is not about any particular triangle with a specific shape or size.  The logical argument

  1. If p, then q;
  2. q is true;
  3. therefore q is true 

is a valid argument no matter what particular propositions we plug into p and q.  Reason is thus truly universal: The same logico-mathematical rules govern thought regardless what cultural or era specific content is thought about.  

Psychology can, then, be the universal science of the mind-as-reason just as physics is the universal science of nature as matter-in-motion.  Cognitive science marries the Classical view of mind as rational calculus with the Scientific Revolution’s idea of the world as a machine.  People think with evolved meat-machine brains, and computers think with artificial silicon brains, and cognitive science is about the logical programs that control both of them.  While people in different cultures think about different topics, and may even have different values, the course of their thinking is determined by the universal laws of reason, and psychology is the science of those laws.  Associationist conceptions of the mind dispense with logic, but share the notion that the rules governing the mind — Hume’s “gravity of the mind” of association — are the same everywhere and in all people, indeed in all animals.  

Counter-Enlightenment thinkers, on the other hand, defended the particularities of culture and language.  Herder, for example, thought that because different languages had different grammars and concepts, that speakers of different languages would think in different ways.  Against the philosophes, who thought that human nature was everywhere and in every period much the same, Herder insisted that the peoples of different cultures and epochs could vary tremendously in how they thought and acted.  With regard to ethics, Herder rejected Kant’s proposal that moral decisions were based on reasoning from abstract moral premises, arguing that moral decisions derived more from feeling than from reason.

Herder’s viewpoint throws cold water on the ambition of psychology, or any of the so-called social sciences to be universal sciences along the lines of physics.  If reasoning varies from culture to culture and from era to era, and if morality is rooted in sentiment more than reason, then there may be no universal laws of human behavior, or they may be so few (e.g., all people get hungry) as to be scientifically uninteresting.  Or, perhaps, there are laws of human thought and action, but they are different in different cultures, and are not universal like the law of gravity. 

Forethoughts.  The various social sciences will begin to emerge in the nineteenth century, and this battle between the universal and the particular will shape debates about their proper methods and goals.  On the one side will be the universalists, primarily British and French, who will maintain the Unity of Science: All sciences, whether of the physical or human worlds, aim at universal law use the same methods, and should develop the same sorts of theories.  On the other side will be particularists, primarily German, who will say that human and natural sciences are radically different in method, theory, and ultimate ambitions.  Unlike the natural sciences, which predict and control nature, the human sciences interpret human thought and behavior within its meaning-giving cultural context.

Variations on the Cartesian Paradigm: Dualism and its Place in Science

Lecture 14.  October 7 and 13.

Afterthoughts.  The second aspect of the Cartesian Paradigm to which I want to draw special attention is its substantial dualism, the claim that body and mind (or soul) are separate things: res extensa and res cogitans.  Dualism as such, of course, is not new.  The Bronze Age Greeks were dualists to a degree, Pythagoras, Plato, and the Neoplatonists were dualists.  Aristotle was a dualist, but not a substantial dualist, because he did not say that soul was a thing.

What made Descartes’ dualism different from these earlier substantial dualism lies less in his conception of the soul, than in his conception of matter.  The Scientific Revolution was developing a powerful, detailed, and new conception of the material world as a machine, and thus Descartes proposed that animal and human bodies are likewise machines.   Human beings, then, must be seen as machines inhabited by souls that interact with them, raising the problems of interaction noted in the Lecture 12 post.

What emerge in the eighteenth century are alternatives to Cartesian dualism, along with alternatives to his conception of consciousness (Lecture 13 post).  There are 3; in each, one aspect of Descartes’ own dualism is rejected as an illusion.  The first to emerge is psychophysical parallelism, which we discussed in class in connection with Leibniz.  Parallelism retains the separation of mind and body (it’s a dualism), but says that the apparent interaction between them is an illusion: Mind and body are synchronized, like 2 synchronized swimmers, but, like the swimmers, they are not causally connected.

The other two alternatives are monisms, which means that they say only one thing exists, the mind or the body, but not both.  One form of monism is idealism, which we find in different forms in Berkeley and Kant. In ontological idealism, the material world does not exist — though there are many, many variations on idealism.  They will not concern us much, because the more influential form of monism in psychology, especially American psychology, and in contemporary thought more broadly, is materialism.  We have met materialism in Hobbes, La Mettrie, and in the French naturalists of the Enlightenment Project.  Materialists hold (like the atomists) that only matter and space exist in reality, that there is no soul, and that therefore the mind (and the appearance of mind-body interaction) is some sort of an illusion.

Forethoughts.  Together with the problems regarding the privacy of consciousness and the accuracy of introspection, Cartesian materialism helped push psychology towards behaviorism.  Parallelism, which was quite popular among psychologists of the founding generation, says that while mind exists, it does not do anything.  Materialism says that mind is an illusion.  Thus to define psychology as the study of the mind — and remember, in the Cartesian version mind = consciousness — is to define it as the science of something pointless or as the science of nothing at all.  As we will see, evolution adds a new aspect to the problem of mind and consciousness — is it adaptive?  The Cartesian paradigm concerning mind and consciousness, already present as psychology’s working framework, is pre-set to answer, “No, it’s not.”

Variations on the Cartesian Paradigm: Consciousness and its Place in Science

Lecture 13.  October 2 and 8.

Afterthoughts.  In the last post, I discussed two aspects of the Cartesian Paradigm that will cause problems for doing psychology as a science within it.  In this one, I will elaborate on one of them, the Cartesian conception of consciousness as developed by thinkers we are just taking up, the Scottish Realists and Kantian Critical Idealism.  All three variations on the Cartesian theme, Descartes’, Reid’s, and Kant’s pose serious challenges for psyche-logos as a science.

The Cartesian challenge we considered in the last post.  If consciousness is private, then studying it is much more problematic than studying the physical world.  

Realism poses a different challenge.  If there is no private realm of ideas, then the subject matter of psyche-logos would seem not to exist.  There is the external physical world, there are organisms, including people, who respond to and act on the physical world, but there is no inner world of ideas to study, and introspection is an illusion.  Moreover, if there is no world of ideas, questions such as Hume’s about the principles that govern the world of ideas are moot.  If there is no mind, there is no “gravity of the mind” to theorize about.

Kantian idealism, as we’ve seen, straightforwardly concludes that psychology, defined as the study of consciousness, cannot be a science.  While idealism admits that ideas exist and therefore might be introspected, such study cannot rise to the status of science.  The ideas populating consciousness are the end product of cognitive processes that cannot be subjected to scientific scrutiny.  In addition, because ideas are produced by the processes of the Transcendental Ego, there will be no “gravity of the mind” acting on ideas, as Hume proposed.  On this view, introspective descriptions of consciousness are more like butterfly collecting or bird-watching than science.  One can describe particular butterflies, birds, or conscious sensations, but that is all.  Explaining experience requires penetration of the Transcendental Ego, which, on Kant’s view, can’t be done.

Forethoughts.  Each of these three variations on the Cartesian Paradigm leads inevitably to redefiningscientific psychology (it will be important to remember that qualification) as the study of behavior.  Descartes’ own position will lead to methodological behaviorism.  Methodological behaviorism says, with Descartes, that consciousness exists and is private.  But, it then argues, because consciousness is private, it is not a fit subject for scientific investigation.  Any science that concerns itself with people must study what’s public, i.e., human behavior, not what’s private, human consciousness.  Kant himself reached a similar conclusion, as we have seen, endorsing his anthropology as a behavioral science of human beings.  Realism will lead to B. F. Skinner’s radical behaviorism.  If there are no ideas, only the world and organisms’ responses to and actions on, the world, then psychology becomes the study of the relationship between the the environment and the behaving organism.  Mental events drop out of the picture.

The Cartesian Paradigm

Lecture 12.  October 2 and 8.

Afterthoughts.  I talked about a Cartesian Paradigm, or Framework, that would guide scientific psychology for much of the twentieth century.  Here I want to amplify two aspects of the paradigm that will be especially important and trouble-making as we move through the rest of the course.

The first aspect is Descartes’ consideration of the mind-body problem and his particular solution to it, interactive dualism.  Most people share an intuition that there is something unique about people that sets us off from things and from the other animals, and we have seen how the Greek philosophers articulated this intuition in different ways.  However, Cartesian dualism is different from Greek dualisms, especially Aristotle’s, in important ways, and I want to stress here how Descartes’ situation is different from Aristotle’s (or all premodern thinkers) not so much because of his conception of mind or soul, but because of the new conception of matter as machine ushered in by the Scientific Revolution.

The key distinction for Descartes is between the soul and the machine-body, but for Aristotle (and the Bronze Age Greeks, too) the key distinction to be drawn was between the living and the nonliving.  For Aristotle, soul was the presence of life, in plants, animals, and humans alike.  The soul was not a thing apart from the living body, but defined the essence of each kind of creature, animated it, and gave it purpose: Soul was form, body was matter.  Soul was life-process, and what distinguished each grade of soul were the processes unique to it: animals had sensation and movement, to which humans added the ability to formulate universal truths.

Descartes, however, had to jettison the idea that plants and animals had souls, because in Christian thought only humans have souls, and he came to regard all physical things, including plant, animal, and human bodies, as machines whose various movements could be explained in the same mechanical terms as the movements of a clock or of the new Newtonian clock-universe.  For Aristotle on the one side there was unformed, unanimated matter and on the other was defining, change-giving form, or soul; for Descartes, on one side were machines, capable of motions of their own, having mechanical causes, and on the other was disembodied nonphysical soul.  Animal behavior had mechanical causes, as seemed clear from Vaucanson’s Duck and other clever automata.  Most importantly, animals had internal cognitive-mechanical processes too, responsible for sensation, awareness, imagination, memory, and learning, things traditionally associated with soul.  But for Descartes, these were no longer life-processes of the soul, as for Aristotle, but mechanical processes of the presumed reflexive gears, springs, and wheels of the nervous system and brain.  Soul was limited to one arena, consciousness, and found in only kind of creature, human beings.

The second critical aspect of the Cartesian Paradigm was the creation of the private realm of consciousness that flowed from the new scientific withdrawal of soul from the material world.  Ideas existed in consciousness only (and animals did not and could not) have them.  Because there seemed to be a New World of consciousness, it invited exploration and study with a special tool for making the voyage, introspection.  Thus was created the idea of a science devoted to consciousness, psyche-logos, the science of the soul.

Forethoughts.  We will soon see the problems raised by this new definition of human science; indeed, we have already met one in Princess Elizabeth’s observations about the difficulties of claiming that a machine can act on spirit and spirit on a machine, the problem of interaction.  What I want to point out here is a more basic problem for psychology defined according to the Cartesian framework: It makes doing psychology as a science nearly impossible, especially as science, especially physiology advances, and as the enterprise of science itself becomes more precisely formed in the nineteenth century.  

So little is left to soul in the Cartesian view that it will become tempting to simply eliminate the concept altogether and say that men are machines as are all animals, albeit more complicated ones.  If one takes this step, then since there is no psyche there can be no psyche-logos anymore then there can be Zeus-logos.  

On the other hand, if one retains the idea of consciousness, other problems arise.  If consciousness is real, but does not interact with body (the view of psycho-physical parallelism we’ll soon meet), then one can have a disciplined study of consciousness, but its point becomes unclear, especially when science is linked to application.  If consciousness exists but does not do anything, its study can have little, if any, practical pay-off.  In addition, introspection is necessarily a private exploration of one person’s consciousness, and even if it’s done in a lab with the best intentions and the tightest methodological controls, the resulting data are tainted with subjectivity, including the possibility of individual differences, the powers of suggestion and expectation, and the difficulties of verifying the accuracy of introspective reports.  While disputes of course arise in any science over the validity of data, the data of introspection will seem especially dodgy, and the enterprise of psyche-logos, while logically possible, will seem to many not to be worth the effort.

Note that these problems would not have arisen for an Aristotelean psyche-logos, because in Aristotle there is no private world of non-physical ideas populating a non-physical soul.  There is, of course, experience in Aristotle’s psychology, but experience is the process of sensation and perception; it is not the collective set of ideas present at some moment in consciousness.  There are no ideas needing description and reduction to lawful order.

That is why my last slide on Descartes said that while he invited the creation of psyche-logos, he made its practice impossible, even paradoxical.

Psyche and Psychology

Lecture 4.  September 2 and 8.

Afterthoughts.  The deepest problems of biology and psychology began with explaining the difference between the living and the non-living by positing the existence of an entity, the psyche, that inhabits the bodies of living creatures.  In biology, this line of thought led to vitalism, the idea that living tissue possesses a vital “spark of life” making it absolutely and decisively different from mere matter.  In psychology (note we still call our field after the breath of life), it leads to the problem of dualism.  It is clear that animals and people are material beings in some sense like rocks–drop me and a rock off of a tall building and we both break.  And it is also clear that animals and people are different — I move sense the world and respond to it, the rock does not.  The problem arises when we explain the difference by saying I (or an animal) possess a secret thing inside, a psyche,  responsible for my sensing and behavior.  If the psyche is a thing, rather than a process, we immediately want to know what it looks like, how it works, how it controls the body, whether it can exist without a body, and so on, and these questions become the subject matter of psyche-logos, the study of the soul.  But suppose that there is no such thing?  Can there be a science about nothing?

Forethoughts.  The problems posed by dualism will be important in understanding Plato and Aristotle. Plato will follow Pythagoras and accept the idea that the soul can exist without the body, that it ought to exist without the body, and, going past the Bronze Age definition of psyche as a breath of life, hold that the soul is the essence of each individual person, and that all, not just a few, are eternal.  This point of view will help give Plato’s philosophy its rather religious, otherworldly, and puritanical cast: The Good is not to be found in this life but in heaven (Plato’s upward hand in Raphael’s painting).  Aristotle, on the other hand, will to a large degree accept the Bronze Age collection of mini-souls, but will resist the notion that souls are things, preferring to see them as life-processes rather than as indwelling entities.  Moreover, Aristotle does not see the body as a dangerous tomb wherein the soul is stored between happy existences in heaven, but as the proper and necessary condition of living a full life (Aristotle’s downward gesture in The School of Athens).  Aristotle’s psychology could have avoided the problems that will plague dualism (and psychology) well into the twentieth century, but, as we will learn, dualism trumps naturalism in the history of psychology.