A splendid example of a wrong idea that persisted for nearly half a century (from 1610 to 1655) is the belief that Saturn was an odd configuration of either one, two, or three bodies orbiting around each other, with no hint that it had rings. 

Galileo's started the error with his earliest telescopic observations of Saturn in 1610, after which he wrote to Johannes Kepler: "Altissimum planetam tergeminum observavi," "I have observed that the farthest planet is threefold." He then explained what he meant: "This is to say that to my very great amazement Saturn was seen to me to be not a single star, but three together, which almost touch each other."

Galileo's error is instructive for an understanding of the interplay of data and theory, and when it came to Saturn, Galileo lacked them both. Data: Saturn is twice as far away as Jupiter, thus what few photons of light there were streaming through the cloudy glass in his little tube made resolution of the rings problematic at best.

Theory: There was no theory of planetary rings. It is at this intersection of nonexistent theory and nebulous data that the power of belief is at its zenith and the mind fills in the blanks. Challenged by a fellow astronomer who suggested that perhaps it was one oblong object rather than three spheres, Galileo boasted of his own superior observational skills, and that "where perfection is lacking, the shape and distinction of the three stars imperfectly seen. I, who have observed it a thousand times at different periods with an excellent instrument, can assure you that no change whatever is to be seen in it."

Such is the power of belief that Galileo went to his grave believing not what his eyes actually saw but what his model of the world told him he was seeing. It was literally a case of I wouldn't have seen it if I hadn't believed it. It wasn't until 1659 and the publication of the Dutch astronomer Christiaan Huygens's great work Systema Saturnium that it became common astronomical knowledge that Saturn had rings.

Perhaps the most embarrassing example from 20th Century physics of a false but widely held belief was the claim that von Neumann had proved in his 1930 text book on the mathematical foundations of quantum mechanics that hidden variables theories are impossible. These would be theories that give a complete description of individual systems rather than the statistical view of ensembles described by quantum mechanics. In fact de Broglie had written down a hidden variables theory in 1926 but abandoned work on it because of von Neumann's theorem. For the next two decades no one worked on hidden variables theories.

In the early 1950's David Bohm reinvented de Broglie's theory. When his paper was rejected because von Neumann proved what he claimed impossible, he read and easily found a fallacy in the von Neumann's reasoning. Indeed, there had been at least one paper pointing out the fallacy in the 1930s that was ignored. The result was that progress on hidden variables theories in general, and de Broglie and Bohm's theory in particular, was delayed by several decades.

An example in economics is the notion that an economic markets can usefully be described as having a single unique and stable equilibrium, to which it is driven by market forces. As described by neoclassical models of markets such as the Arrow-Debreu model of general equilibrium, equilibrium is defined as a set of prices for which demand for all goods equals supply, as a result of each consumer maximizing their utility and each producer maximizing their profit. A basic result is that such equilibria are Pareto efficient, which means no one's utility can be increased without decreasing some body else's utility. Furthermore, if the economy is in equilibrium there are no path dependent effects, moreover it can be argued that market prices in equilibrium are perfectly rational and reflect all relevant information.

If equiilibrium were unique, then one could argue that the most ethical thing to do is to leave markets free and unregulated so that they can find their points of equilibrium where efficiency and utility are maximized. This kind of thinking to some extent motivated choices about leaving financial markets under-regulated resulting in the recent economic crisis and current difficulties.

However, it was learned in the 1970s that even if efficiency and equilibrium are useful notions, the idea that equilibria are unique is not true in generic general equilibrium models. The Sonnenschein-Mantel-Debreu Theorem of 1972 implies that equilibria are in general highly non-unique, and it is not difficult to invent models in which the number of equilibria scales with the number of producers. But if there are multiple equilibria, most will not be stable. Moreover supply and demand are balanced in each of the many equilibria, so market forces do not suffice to explain which equilibria the market is in or to pick which would be preferred. The consequence theoretically is that path dependent effects which determine which of many the equilibria the market is in must be important, the political consequence is that there is not an ethical argument for leaving markets unregulated. Since then some of the more interesting work in economics studies issues of path dependence and multiple equilibria.

I cannot comment on why economists made the mistake of thinking about market equilibrium as if it were unique. I do think I have some insight into why a false belief about the possibility of alternatives to quantum mechanics could persist for more than two decades. During this period there was rapid progress in the application of quantum mechanics to a wide set of phenomena from astrophysics to nuclear and solid state physics.

Meanwhile the most popular interpretation of quantum mechanics was Bohr's, which is now hardly taken seriously by anyone. Those who concentrated on the foundations of the subject were left behind, especially as it was convenient for the progress that was being made, to believe that the foundations were surer than in fact they were. Perhaps there are periods in science where it makes sense for most scientists to sweep foundational worries under the carpet and make progress on applications, postponing the inevitable reckoning with the inconsistencies to a time when there are better hints from experiment.

We have acted, with good reason, as if human beings are all alike. And given the history of eugenics this has been a good and rational position and policy. But we are entering an era where we recognize that there are more and differences in how a particular medicine affects particular groups of people. Same of foods, pollutants, viruses, and bacteria.We are beginning to recognize we react, and are at differential risks, of catching diseases like AIDS, malaria, anemias. And just this month we began to get a glimpse of the first thousand human genomes. These will soon number in the hundreds of thousands. Are we ready should these initial gene maps show that there are real and significant differences between groups of human beings?

Why does it take so long to accept new views even when the evidence is clear? Wittgenstein tells the following anecdote (I presume to show that first impressions about why views change are generally wrong):

Two philosophers meet in the hall. One says to the other, Why do you supposed people believed for such a long time that the sun goes around the earth, rather than that the earth rotates? The other philosopher replies, Obviously because it looks as though the sun is going around the earth. To which the first philosopher replies, But what would it look like if it looked like the earth was rotating?

I think it's particularly fascinating to look at how scientific beliefs about the functioning of the human brain have progressed through a long series of misconceptions.

Aristotle couldn't believe that the brain, an inert grey mass, could have anything to do with thought; he assumed that the heart, hot and pulsing, must be the source of cognition, and that the brain's function was simply to cool the blood.

Descartes assumed that the brain, with its aperture-like "cavities and pores," was, along with the heart, part of an elaborate hydraulic system that controlled the flow of "animal spirits" through the "pipes" of the nerves. More recently, there was a longstanding belief that the cellular structure of the brain was essentially fixed by the time a person hit the age of 20 or so; we now know, through a few decades' worth of neuroplasticity research, that even the adult brain is quite malleable, adapting continually to shifts in circumstances and behavior.

Even more recently there's been a popular conception of the brain as a set of computing modules running, essentially, genetically determined software programs, an idea that is now also being chipped away by new research. Many of these misconceptions can be traced back to the metaphors human beings have used to understand themselves and the world (as Robert Martensen has described in his bookThe Brain Takes Shape).

Descartes' mechanistic "clockwork" metaphor for explaining existence underpinned his hydraulic brain system and also influenced our more recent conception of the brain as a system of fixed and unchanging parts.

Contemporary models of the brain's functioning draw on the popular metaphorical connection between the brain and the digital computer. My sense is that many scientific misconceptions have their roots in the dominant metaphors of the time. Metaphors are powerful explanatory tools, but they also tend to mislead by oversimplifying.

The closest thing to a persistent flat earth belief in psychology is probably the view that experiences in the first five years of life largely shape the personality of the adult. (The child is father to the man, as Freud said). It's now clear that experiences that affect brain development, such as some viral diseases or some head injuries, can indeed change adult personality. Also, extreme conditions that endure for years or that interfere with the formation of early attachments (e.g., an abusive parent) can also have lasting effects. But the idea that relatively short-lived experiences in the first few years — even traumatic ones, and even short-lived sexual abuse — will have powerful effects on adult personality... this just doesn't seem to be true. (Although such events can leave lasting traces on older children). Personality is shaped by the interaction of genes with experience; psychologists and lay people alike long underestimated the power of genes, and they spent too much time looking at the wrong phase of childhood (early childhood), instead of at the developmental phases that matter more (i.e., the prenatal period, and adolescence).<

Why is early childhood such a draw when people try to explain adult personalities? I think it's because we think in terms of stories, and it's almost impossible for us NOT to look back from Act III (adulthood) to early childhood (act I) when we try to explain someone turned out to be a hero or serial killer. In stories, there's usually some foreshadowing in act I of events to come in act III. But in real life there is almost never a connection.

The belief (or maybe, more accurately, the unstated intuition) that objects must be in direct contact to influence one another.

In the 17th century, that led skeptics to scoff at Newton's theory of gravity. Proper science was supposed to map how matter pushes against matter to cause various effects. Yet in this theory there was no physical contact, just spooky action at a distance. Almost a century after Newton, rival theories of gravity were still being proposed to remedy this defect.

Similarly, many scientists (including Newton) long theorized about aether, the substance that carries light, in part because, well, if light arrives, it must be borne bysomething. Perhaps the modern incarnations of this belief are claims that psychological and biological sciences won't be really sound until they can be restated in terms of chemistry or physics, ie, as statements about matter interacting with itself.

The reason the belief persisted? In my first example, I believe, it was because it sounded, in the context, "more scientific" than its predecessors and its challengers. To an advanced 17th century thinker, for example, thinking that the sun can influence the Earth without physical contact probably smacked of medieval physics. The best and brightest had recently overthrown these notions that objects fell without a material cause, so why should we go backwards?

I think this is a common reason for the endurance of theories in the face of contrary evidence: The theory has the patina of rigor and seriousness, while alternatives are, rightly or wrongly, associated either with (supposedly) defunct ideas or with intellectual confusion. We don't want to march backwards and we don't want to get lost, so we'd better stick with what we have.

To bring this back round to your own work (and to fend off accusations that I've built a straw man), I have been told more than once that "rational economic man" theories of behavior, flawed as they are, at least have the virtue of coherence and rigor, and therefore can't be jettisoned. "It may be flawed science, but it's the only science we have" — I think that has been a motive for clinging to beliefs long past the point where we, from our vantage point, think they were justified.

My favourite example is the hunt for the "élan vital" or life force. People seemed to think that — given living things behave so very differently from non-living things — there must be some special underlying force or substance or energy or something that explains the difference, something that animates a living body and leaves the body when it dies.

Of course many people still believe in various versions of this, such as spirits, souls, subtle energy bodies and astral bodies, but scientists long ago gave up the search once they realised that being alive is a process that we can understand and that needs no special force to make it work.

I think this was believed to be true for two reasons :

1. Explaining how living things work is not trivial — it has required understanding heredity, homeostasis, self-organisation and many other factors.

2. (perhaps more important) Human beings are natural dualists. From an early age children begin thinking of themselves not as a physical body but as something that inhabits a physical body or brain. We feel as though we are an entity that has consciousness and free will even though this is all delusion. I suggest that this delusion of duality is also the underlying cause of the hopeless hunt for the life force.

Believing that people believed the Earth was flat is a good example of a modern myth about ancient scientific belief. Educated people have known it was spherical (and also how big it was) since the time of Eratosthenes. That is pretty close to the beginning of any system of thought that could reasonably merit being called scientific...

One that was long thought to be true, but isn't, is the spontaneous generation of life. I've never quite understood how that squared with life being divinely created. But the whole pre-Pasteur thing was definitely a widely held, incorrect belief...

In Europe it used to be thought that what are now understood to be prehistoric stone tools originated naturally rather than technologically. In line with other objects displaying regular forms, such as ammonites or hail stones, and in view of the fact that things like meteorites do sometimes fall out of the sky, the facetted tear-drops of flint that we now call Acheulian hand axes were believed to coalesce in rain clouds.

By contrast, barbed and tanged arrowheads were imagined to be supernatural – 'elfshot'. The overarching Biblically-based metaphysic of a world not yet 6000 years old denied a plausible timeframe for any radically different human past.

It took two things for the natural / supernatural categories to be replaced.

First, encounters during the 'Age of Discovery' with indigenous peoples without the use or knowledge of metals allowed the mystery objects to be viewed analogously (a perspective latent, yet warped, in the 'elfshot' idea).

Second, the application of uniformitarian principles in geology challenged the diluvial (flood-produced) explanation of landforms and pointed to a very ancient earth. Thus a human antiquity of potentially vast length became imaginable in which prehistoric European counterparts to the ethnographically known 'stone age' societies could be postulated.

A persistent belief is that human symbolic intelligence is the highest form of intelligence around. This leads directly to both creationism and good old-fashioned AI which seeks to model cognition using Lisp programs.

Evolution can design machines of such great complexity that the space shuttle with half a million parts looks like a tinker toy construction. In order to explain the design intelligence of evolution, most Republicans are convinced that a superintelligent creator was involved. Developmental intelligence which manufactures machines with 10 billion moving parts without any factory supervisors is another area where nature outstrips the best human performance. Immunological Intelligence, telling self from non-self, is another AI-complete problem. And human intelligence itself is so vastly complex that we've made up stories of conscious symbol processing, like logic and grammar, to try to explain what goes on in our heads

As classicist, I feel I know too many examples! Ancient medicine and ancient astronomy in particular were full of truths, quite true and valid within the framework within which constructed, that now appear as utter nonsense. I would put at top of my list, however, the science of astronomy — not for the Ptolemaic mathematical workings-out, but for the solid, serious, scientific astrological content. That is to say, it's a beautiful example of a paradigm, in Kuhnian terms, that made perfect sense at the time, that was the foundation for many further advances, that led to undoubtedly serious science, that validated itself by e.g. the way it allowed you to predict eclipses (how could it not be science?), and that just fell apart at the touch of a serious thought. To compare large with small, I would put it next to the science of ulcer medicine 60 years ago, which made similar perfect sense and was all driven by diet and stress and was a continually refining science — falling apart more or less isntantaneously, what, 25 years ago, with the discovery of the link to H. pylori. What the two have in common is the focus on phenomena (that is, the things that appear, the surface data) produces science, but each time you go a step beneath phenomena to mechanisms, new science happens. That's when the impossible becomes possible.

Vitalism, the belief that living things embody a special, and not entirely natural, animating force or principle that makes them fundamentally different from nonliving entities. (Although rejected by scientists, I would hazard the guess that vitalism is not entirely dead today among many members of the general public.) This belief's persistence over the ages is explained by the obvious observable differences between life and nonlife.

Living things move about under their own power, they grow, multiply, and ultimately die. Nonliving objects like stones, beer bottles and grains of sand don't do any of that. It's the overwhelming nature of these perceptible differences that accounts for the belief's longevity. In addition, there is still no universally accepted scientific explanation of how life arose, which only adds to the impression that there's something scientifically unexplainable about life.

Intelligent design... special creation... the reason... a long age of the earth is so long that people didn't realize that evolution could occur.

Many (but not all) scientists assumed the far side of the moon would turn out to look much the same as the side we are familiar with. "I was very enthusiastic about getting a picture of the other side of the moon," Herbert York, former advisor to President Eisenhower, told me in 1999. "And there were various ways of doing it, sooner or later. And I argued with Hornig [Donald Hornig, Chairman of the President's Science Advisory Committee] about it and he said, 'Why? It looks just like this side.' And it turned out it didn't."

For many centuries, most scientists and philosophers believed that dead or inanimate matter could quickly transform itself into living beings, just as the reverse can occur quite rapidly. This belief, rapid spontaneous generation, was supported by simple observation of common events. Fireflies emerged from the morning dew, bacteria appeared in sterilized broths and small animals arose from mud at the bottom of streams and ponds.

In Shakespeare's "Antony and Cleopatra" Lepidus told Antony "Your serpent of Egypt is born of the mud, by the action of the Sun, and so is your crocodile." Among the notables who endorsed this theory were Aristotle, Thomas Aquinas, Francis Bacon, Galileo and Copernicus. Many carefully controlled experiments, culminating in the work of Louis Pasteur, were needed to negate this idea.

My favorite example is about science itself. For the longest time scientists didn't believe that their own discipline followed rules, per se, but then Imre Lakatos, Thomas Kuhn, Karl Popper and, my favorite, Paul Feyerabend showed how science was sociology, was prone to enthusiasms, fashions, and dogma, and so on. It was one of the most important realizations of my doctoral program.

There is interesting evidence that many once popular and evidence-resistant scientific belief systems are also developed spontaneously by many children. For example, children seem to develop a "vitalistic" theory of intuitive biology, rather like the Chinese concept of "chi", at around age 5, independently of what they are taught in school. Similarly , school-age children, even those with an explicitly atheist upbringing, develop ideas about God as an explanatory force at about 7, as part of an "intuitive teleology" that explains events in terms of agency.

The psychologist Tania Lombrozo has shown that even Harvard undergraduates who endorse evolution consistently interpret evolutionary claims in a teleological rather than mechanistic way (eg giraffes try to reach the high leaves and so develop longer necks). And we have shown that six year olds develop a notion of fully autonomous "free will" that is notoriously difficult to overturn. There is also a lot of evidence that scientific theories are built out of these everyday intuitive theories.

If, as we think, children use Bayesian techniques to develop intuitive theories of the world, based on the evidence they see around them, then it might , in some sense, be rational to hold on to these beliefs, which have the weight of accumulated prior experience. Other scientific beliefs, without a history of everyday confirmation, might be easier to overturn based on just scientific evidence alone.

Creationism's step sister, intelligent design, and allied beliefs have been held true for some time, even as the mountain of evidence supporting an evolutionary explanation for the history and diversity of life continues to grow. Why has this belief persisted? There are political and religious reasons, of course, but history shows than neither politics nor religion require a creationist belief in intelligent design.

I think the deeper answer lies elsewhere, in the way children categorize the world in to a hierarchy of types of inanimate and living things (and for that matter types of people), and the rigid categorization this leaves in adults that stands in the way of accepting biological explanations that show the hierarchy can develop from natural laws including randomness,and categories may originate and change by natural laws within a hierarchical structure. Could a draw poker hand improve without divine intervention? Could Plato's precept of ideals have survived a trip to Art Van's?

Overthrowing a presumption of symmetry, Broca revealed in 1862 that the left forebrain alone subserves language. The left hemisphere’s many specializations were cumulatively uncovered in the course of the next hundred years. Yet the "minor" right hemisphere was not similarly investigated until the 1960s. How could the plentiful specializations of the right hemisphere have been so long overlooked? The problem was not technological. The right hemisphere’s specializations were ultimately revealed by the same methods that had uncovered those of the left. What finally oriented investigators to the profuse specializations of the right hemisphere: spatiotemporal, emotional, interpersonal, creative?

Perhaps it was culture change (Kinsbourne 2000). Rigidly hierarchical thinking about human affairs prevailed: master/slave, boss/worker, king/subject, priest/sinner, God/angel, along a continuum of power, influence and assumed merit, projected to notions about the brain. Language, and the left hemisphere were placed at the peak. Simpler functions shared with other animals, were conceived as bilaterally represented. Thus the right hemisphere was denied its own specializations.

As the great empires fragmented into patchworks of independent states after World War Two, vertical value rankings no longer seemed self-evident or sufficient. Cultural constructs expanded to encompass horizontally interactive, collaborative organization (Crumley 1995). This upheaval of ideas at last permitted focus on the right hemisphere as a highly specialized collaborator of the left. In time it overthrew the antiquated notion of the cerebral network as a tangle of centers and connections, and recognized it as a heterarchical democracy (McCulloch 1945):  uncentered, unsupervised, parallel, and self-organizing.

Unquestioned and even unconscious cultural premises obstructed the natural progress of discovery. Perhaps "self-evident" but false culture-based assumptions still hold us up.

Richard Thaler seems to think that the concept of a flat earth was widely held for a long time. This is not really correct. Mariners have long understood that the earth is strongly curved and possibly a sphere. Ships disappear down over the horizon (I once saw this effect on the Chesapeake bay and was shocked how fast the hull of a giant container ship dropped out of sight while the top of the superstructure was still easily visible). Polaris gets lower on the horizon as one sails south and eventually disappears and so on. Over 2000 years ago the circumferance of the planet was pretty accurately calculated by Eratosthenes using some clever geometry and sun angle measurements. This knowledge may have been lost in the west in the dark ages, but was well known to the Euroelites after the improved communications from Constantinople, Alexandria etc after the Crusades.

When Columbus was trying to get a government to cough up the money for his trip west he was not trying convince patrons that the planet was a sphere. The problem was that the experts told the people with the money that the distance from Europe and Asia across the super ocean separating them was 14,000 miles with no visible means of logistical support during the voyage (the perfect Bible did not mention extra continents being in the way). However, some works had come out saying that Eratosthenes had messed up and the planet was much smaller (I've heard this was based on Biblical passages and Columbus was very devout, but am not sure about that). Columbus figured it was 3-4000 miles to the west, a skip and a hop compared to the horrendous around Africa route. When the Spanish monarchs finally kicked the last Muslims out of Iberia and were having fun picking on Jews they decided what the heck and see what this Columbus fellow could do, the cost was just three little cargo vessels and their crews.

The story about the crews getting upset about sailing off the edge of the earth is probably a myth since they knew better. That Columbus was fighting the false knowledge of the flat earth apparently was invented in the late 1800s in an effort to make him a great American symbol of the progress of science over superstition associated with the 1892 celebrations.

As far as a distinct example of lots of people believing in something that is scientifically wrong the best example I can think of are the various creation myths. This occurred not only before the advent of modern science but continues in the form of various forms of creationism.

Caloric, phlogiston, and ether immediately come to mind, but I'm particularly fond one consequence of Aristotelian mechanics: the assertion that there is no such thing as a vacuum.

The concept of the void conflicted with the way that Aristotle conceived of motion; admitting a void into his universe quite simply broke all of his models about the nature of matter and the way objects move. (A rock, say, suspended in a vacuum, would not be able to fall to its proper place at the center of the world as his laws said they must.)

In the West, the consequent misconception — that nature so abhors a vacuum that it can not exist under any circumstance — lasted until Torricelli and Pascal disproved it in the 17th century.

For years I believed the Government's insistence that UFO's did not exist until I saw one under circumstances that could leave no doubt. Subsequently over many years I have seen three more. Being a scientist and professor at U.C. Berkeley, I quizzed many graduate students, asking them if they think they have seen UFO's would they come to my office and tell me about them. To my surprise, several of them did, and some went on to teach at various universities such as CalTech, and Johns Hopkins. They found, as I have, if a person hasn't seen one, he/she won't believe you. I have convinced only one scientist, and this was by giving him two excellent books on the subject which he read carefully, He came to me and said, "I am now a believer, but why this government secrecy?" I replied that I didn't know but that it must be extremely important to some branch of the government in the military.

"This laxe pithe or marrow in man's head shows no more capacity for thought than a Cake of Sewet or a Bowl of Curds."

This wonderful statement was made in 1652 by Henry More, a prominent seventeenth-century British philosopher. More could not believe that the brain was the source of thought. These were not the ravings of a medieval quack, but the argument of a brilliant scholar who was living through the scientific revolution. At the time, the state of science made it was very easy for many people to doubt the capacity of the brain. And if you've ever seen a freshly dissected brain, you can see why. It's just a sack of custard. Yet now, in our brain-centered age, we can't imagine how anyone could think that way

1. For years, running shoe companies have assumed without evidence that more is better, that thicker padded soles are better at preventing injuries in runners. In the 70s, shoe soles grew Brobdingnagian. Now, recent research confirms that running barefoot and landing on your forefoot, on any surface, even one as hard as the road to hell, produces less shock than running and unavoidably landing on your heels in rigid padded stabilized shoes.

2. For years optometrists have given small children spectacles at the first hint of nearsightedness. But ordinary unifocal lenses modify not only their accommodation to distance vision but to near vision too, where they don't need help. Now there is evidence that giving near-sighted kids bifocals that correct only their distance vision and not their close-up vision seems to make their nearsightedness progress less rapidly.

Phrenology and lobotomy. Even when these were not scientific paradigms, they clearly illustrate how science affects people's life and morality. For those not engaged in the scientific work, it is easy to forget that technology, and a great part of the western contemporary culture, results from science. However, people tend to interpret scientific principles and findings as strange matters that have nothing to do with everyday life, from gravity and evolution, to physics and pharmacology.

Phrenology is defined as the "scientific" relation between the skull's shape and behavioral traits. It was applied to understand, for example, the reason for the genius of Professor Samuel B. F. Morse. However, it was also applied in prisons and asylums to explicate and predict criminal behaviors. In fact, it was also assumed that the skull's shape explained incapacities to act according to the law. If you were spending your life in an asylum or a prison in 19th century because of a phrenological "proof" or "argument", you could perfectly understand how important science in your life is, even if you are not a scientist. Even more, if you were going to be a lobotomy's patient in the past century. 

In 1949, Antonio Egas Moniz achieved the Nobel Prize of Physiology and Medicine for discovering the great therapeutic value of lobotomy, a surgical procedure that, in its transorbital versions, consisted of introducing an ice pick through the eye's orbit to disconnect the prefrontal cortex. Thousands of lobotomies were performed between the decade of 1940's and the first years of 1960's, including Rosemary Kennedy, sister of President John F. Kennedy, on the list of recipients; all of them with the scientific seal of a Nobel Prize. Today, half a century later, it seems unthinkable to apply such a "scientific" therapy. I keep asking myself: "what if" a mistake like this one is adopted today as policy on public health?

Science affects people's lives directly. A scientific mistake can send you to jail or break your brain into pieces. It also seems to affect the kinds of moral stances that we adopt. Today, it would be morally reprehensible to send someone to jail because of the shape of his head, or to perform a lobotomy. However, 50 or 100 years ago it was morally acceptable. This is why we should spend more time thinking of practical issues, like scientific principles, scientific models and scientific predictions as a basis for public health and policy decisions, rather than guessing about what is right or wrong according to god's mind or the unsubstantiated beliefs presented by special interest groups.

I would not count flat earth as a wrong theory believed to be true by everybody since e.g. the ancient Greeks thought the Earth was a sphere and had even measured its curvature.

A classic example of a wrong theory is that of Phlogiston, namely the existence of a substance that is released in combustion. There were also variations going by the name of caloric. A second wrong theory is that of a Luminiferous Aether, a substance through which light is transmitted. Chemical experiments disproved the first and e.g. the Michelson -Morley expt. the second.

There are of course also numerous wrong theories/beliefs regarding spontaneous generation of life disproved in the 17th century by Francesco Redi and ultimately by Louis Pasteur in the 19th.

I have a small favorite, the belief that body temperature varied with climate, disproved by the invention in the early 17th century of the thermometer.

In the nineteenth century, many scientists were convinced that the course of nature was totally determinate and in principle predictable in every detail, as in Laplace's famous fantasy of scientific omniscience: "Consider an intelligence which, at any instant, could have a knowledge of all the forces controlling nature together with the momentary conditions of all the entities of which nature consists. If this intelligence were powerful enough to submit all these data to analysis it would be able to embrace in a single formula the movements of the largest bodies in the universe and those of the lightest atoms; for it nothing would be uncertain; the past and future would be equally present for its eyes."

T.H. Huxley even imagined that the course of evolution was predictable: "If the fundamental proposition of evolution is true, that the entire world living and not living, is the result of the mutual interaction, according to definite laws, of the forces possessed by the molecules of which the primitive nebulosity of the universe was composed, it is no less certain the existing world lay, potentially, in the cosmic vapour, and that a sufficient intellect could, from a knowledge of the properties of the molecules of that vapour, have predicted, say, the state of the fauna of Great Britain in 1869."

With the advent of quantum theory, indeterminacy rendered the belief in determinism untenable, and in the neo-Darwinian theory of evolution (which T.H. Huxley's grandson, Julian, did so much to promote) randomness plays a central role through the chance mutations of genes.

Enlightenment Reason and Classical Rationality have been shown over and over in the cognitive and brain sciences to be false in just about every respect. Yet they are still being taught and used throughout the academic world and in progressive policy circles. Real human reason is very different. 

Here are the claims of enlightenment reason, and the realities:

• Claim: Thought is conscious. But neuroscience shows that thought is about 98 percent unconscious.

• Claim: Reason is abstract and independent of the body. But reason is embodied in two ways: (1) we think with our brains and (2) thought is grounded in the sensory-motor system.

• Yet, because we think with our brains and thought is embodied via the sensory-motor system, reason is completely embodied.

• Claim: Reason can fit the world directly. Yet because we think with a brain structured by the body, reason is constrained by what the brain and body allow.

• Claim: Reason uses formal logic. In reality, reason is frame-based and very largely metaphorical. Basic metaphors arise naturally around the world due to common experiences and the nature of neural learning. The literature on Embodied cognition has experimentally verified the reality of metaphorical thought. Real human reason uses frame-based and metaphor-based logics. Behavioral economics is based on this fact.

• Claim: Emotion gets in the way of reason. Actually, real reason requires emotion. Brain-damaged patients who cannot feel emotion don't know what to want, since like and not like mean nothing to them and they cannot judge the emotions of others. As a result they cannot make rational decisions.

• Claim: Reason is universal. Actually, even conservatives and progressives reason differently, and evidence is pouring in that one's native language affects how one reasons.

• Claim: Language is neutral, and can fit the world directly. Actually language is defined in terms of frames and metaphors, works through the brain and does not fit the world directly. Indeed, many of the concepts named by words (e.g. freedom) are essentially contested and have meanings that vary with value systems.

• Claim: Mathematics exists objectively and structures the universe. Mathematics has actually been created by mathematicians using their human brains, with frames and metaphors.

• Claim: Reason serves self-interest. Partly true of course, but to a very large extent reason is based on empathetic connections to others, which works via the mirror neuron systems in our brains.

Given the massive failures of enlightenment reason, widely documented in the brain and cognitive sciences, why is it still taught and widely assumed?

First, it did a great historical job back in the 17th and 18th centuries in overcoming the dominance of the Church and feudalism.

Second, it permitted the rise of science, even though science doesn't really use it.

Third, unconscious mechanisms like framed-based and metaphorical thought are mostly not accessible to consciousness, and thus we cannot really see how we think.

Fourth, applications of formal logic have come into wide use, say in the rational actor model of classical economics (which failed in the economic collapse of 2008).

Fifth, we are taught enlightenment reason in our schools and universities and its failure is not directly taught, even in neuroscience classes. Seventh, most people just think and don't pay much attention to the details, especially those that are not conscious.

Sixth, most people just think and don’t pay much attention to the details, especially those that are not conscious.

Much of liberal thought uses enlightenment reason, which claims that if you just tell people the facts about their interests, they will reason to the right conclusion, since reason is supposed to universal, logical, and based on self-interest. The Obama administration assumed that in its policy discourse, and that assumption led to the debacle of the 2010 elections. Marketers have a better sense of how reason really works, and Republicans have been better at marketing their ideas. The scientific fallacy of enlightenment reason has thus had major real-world effects.

In the early days of the field of Artificial Intelligence, researchers thought that it would not be terribly difficult to implement a vision recognition or language understanding program. According to a July 1966 memo from the MIT Project Mac archive, Seymour Papert announced a summer project whose goal was to construct "a significant portion of the vision system." Other early leaders of AI were also optimistic, including Herbert Simon who was quoted saying in 1965 that "machines will be capable, within twenty years, of doing any work a man can do," and Marvin Minsky, who is attributed with saying "within a generation ... the problem of creating 'artificial intelligence' will substantially be solved."

The importance of these misperceptions is the underestimation of the complexity of the brain.