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How can flies sense mirrors?

How can flies sense mirrors?


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I've noted that flies in my house have no problem landing on even perfectly clean mirrors. Why don't they fly straight into them? Can they sense that there is a surface there, even though they can't see it?


It might be pretty straightforward. Common window/mirror glass is opaque to UV, so as far as the fly is concerned mirrors are just translucent surfaces.

This of course leads to the question of why flies can't see window glass. Maybe the large amount of light passing through at visible frequencies makes it look like a tinted fog to the housefly? Maybe they're trying to fly through mirrors too, but land on their feet and just roll with it?


Insects Can Predict Adverse Weather, Entomologists Say

Curcurbit beetle, shown here, the true armyworm moth and the potato aphid can predict adverse weather conditions. Image credit: Melinda Sullivan and Edward Jones, USDA APHIS.

Entomologists led by Dr Ana Cristina Pellegrino from the University of São Paulo studied mating behavior changes in the curcurbit beetle, the true armyworm moth, and the potato aphid under falling, stable, and increasing air pressure conditions.

When they measured the male beetles’ response to female sex pheromones under the different conditions, they found a significant decrease in pheromone response when air pressure fell compared to stable or increasing pressure.

Furthermore, 63 percent of males started copulating faster in the presence of females during dropping atmospheric pressure, a condition associated with high rains and winds. By contrast, under stable or rising air pressure conditions, all males showed full courtship behavior.

Additionally, the amount that female armyworm moths and potato aphids showed mate-attracting behavior was also measured under the three atmospheric conditions.

The female armyworms’ calling was reduced during decreasing air pressure, but the potato aphid showed reduced calling during both decreasing and increasing air pressure, two conditions that can occur with high winds. In both cases, reduced calling went hand-in-hand with reduced mating behavior.

“The results presented show that three very different insect species all modify aspects of their sexual behavior in response to changing barometric pressure,” explained co-author Dr José Maurício Simões Bento from the University of São Paulo.

“However, there is a great deal of interspecific variability in their responses that can be related to differences in size, flight ability and the periodicity of mating.”


Scientists discover why flies are so hard to swat

(PhysOrg.com) -- Over the past two decades, Michael Dickinson has been interviewed by reporters hundreds of times about his research on the biomechanics of insect flight. One question from the press has always dogged him: Why are flies so hard to swat?

"Now I can finally answer," says Dickinson, the Esther M. and Abe M. Zarem Professor of Bioengineering at the California Institute of Technology (Caltech).

Using high-resolution, high-speed digital imaging of fruit flies (Drosophila melanogaster) faced with a looming swatter, Dickinson and graduate student Gwyneth Card have determined the secret to a fly's evasive maneuvering. Long before the fly leaps, its tiny brain calculates the location of the impending threat, comes up with an escape plan, and places its legs in an optimal position to hop out of the way in the opposite direction. All of this action takes place within about 100 milliseconds after the fly first spots the swatter.

"This illustrates how rapidly the fly's brain can process sensory information into an appropriate motor response," Dickinson says.

For example, the videos showed that if the descending swatter--actually, a 14-centimeter-diameter black disk, dropping at a 50-degree angle toward a fly standing at the center of a small platform--comes from in front of the fly, the fly moves its middle legs forward and leans back, then raises and extends its legs to push off backward. When the threat comes from the back, however, the fly (which has a nearly 360-degree field of view and can see behind itself) moves its middle legs a tiny bit backwards. With a threat from the side, the fly keeps its middle legs stationary, but leans its whole body in the opposite direction before it jumps.

"We also found that when the fly makes planning movements prior to take-off, it takes into account its body position at the time it first sees the threat," Dickinson says. "When it first notices an approaching threat, a fly's body might be in any sort of posture depending on what it was doing at the time, like grooming, feeding, walking, or courting. Our experiments showed that the fly somehow 'knows' whether it needs to make large or small postural changes to reach the correct preflight posture. This means that the fly must integrate visual information from its eyes, which tell it where the threat is approaching from, with mechanosensory information from its legs, which tells it how to move to reach the proper preflight pose."

The results offer new insight into the fly nervous system, and suggest that within the fly brain there is a map in which the position of the looming threat "is transformed into an appropriate pattern of leg and body motion prior to take off," Dickinson says. "This is a rather sophisticated sensory-to-motor transformation and the search is on to find the place in the brain where this happens," he says.

Dickinson's research also suggests an optimal method for actually swatting a fly. "It is best not to swat at the fly's starting position, but rather to aim a bit forward of that to anticipate where the fly is going to jump when it first sees your swatter," he says.

The paper, "Visually Mediated Motor Planning in the Escape Response of Drosophila," will be published August 28 in the journal Current Biology.


Why do insects communicate?

Insects communicate both with organisms of the same species (intraspecific communication) and directly or indirectly with organisms of other species (interspecific communication) for many reasons:

  • Reproduction : to look for a mate, courtship…
  • To identify members of the same species or even to warn other organisms of its own presence .
  • To localize sources of recourses : food, nidification places,…
  • As an alert signal towards potential hazards.
  • To defend territory .
  • As a way to camouflage or to mimic other organisms (Do you want to learn more about animal mimicry? click here!).

The truth about gaze detection

Because the human eye gaze is optimised for easy detection, it is often easy for us to work out whether someone is looking at us. For example, if someone sitting right opposite you on the train is looking at you, you can register the direction of their gaze without looking directly at them. However, it turns out we can only reliably detect such gaze within four degrees of our central fixation point.

However, we can use other cues to tell when someone is looking at us in our peripheral vision. Typically we also rely on the position or movement of their head (such as a turn towards you). We also rely on head or body cues when the potential watcher is in the dark or is wearing sunglasses. But, interestingly, you may not be right about being watched as often as you think. It turns out that in uncertain situations, people systematically overestimate the likelihood that the other person is looking at them. This may be an adaptation to prepare us for interactions that are about to occur, particularly if the interaction may be threatening.

Probably nobody there. J Walters

But what about the feeling that someone outside your field of vision, such as behind you, is watching? Is it really possible to “sense” that? This has long been a source of scientific investigation (the first study on this was published in 1898) – probably because this idea is very popular. Some studies have found that up to 94% of people report that they have experienced the feeling of eyes upon them and turned around to find out they were indeed being watched.

Sadly for those who wish we were X-men, it appears much of the body of research supporting the “psychic staring effect” appears to be suffering from methodological issues, or unexplained experimenter effects. For example, when certain experimenters act as the watcher in these experiments, they seem to be more “successful” at getting people to detect their stares than other experimenters. It is almost certainly an unconscious bias, perhaps due to initial interactions with the experimenter.

Memory biases may also also come into play. If you feel like you are being watched, and turn around to check – another person in your field of view might notice you looking around and shift their gaze to you. When your eyes meet, you assume this individual has been looking all along. Situations where this happens are more memorable than when you look around to find no one looking at you.

So remember – the next time you think someone you can’t see is watching you, it could be your mind playing tricks on you, no matter how real it feels.


Sanitation Treatments - Invade Bio Products

Use Invade Bio Products in the drains. A use of a drain treatment such as Invade Bio Gel Treatment will remove the organic debris, improving santitation.

Invade Hot Spot is a Microbial/Citrus Foam in an easy-to-use 16 oz aerosol. Hot Spot is an aerosol can that contains the same premium microbes and ingredients as InVade Bio Foam. The 360 degree valve allows for foam dispensing in any orientation to easily hit hard-to-reach areas.

If the Phorid flies are breeding in the soil under a concrete slab, the only way to eliminate the infestation is to remove the contaminated soil by breaking through the slab and replacing the soil. Any broken pipes need to repaired. Although this is costly, drilling and treating the infested soil under the slab with residual insecticides does not work.

Remove all organic debris trapped in small cracks and crevices under the legs and bottom edges of kitchen equipment. The debris needs to removed, thoroughly dried and a long lasting caulk applied to seal the crack.

Invade Bio Foam is another another type of Invade Bio product particulary useful in commercial establishments. It is a concentrated bio liquid with the use of a foamer. Invade Bio Foam contains concentrated scum eating, odor eliminating microbes and foaming agent. Use this a part of an integrated pest management tool. Use 1 oz per quart, 4 oz per gallon. Apply using a B&G VersaFoamer HH or sprayer to cracks, crevices and drains where small flies breed. The foam and citrus combination will digest the organic debris present as part of pest management. Ultra-concentrated InVade Bio Foam is mixed with water at a rate of 4 oz per gallon (1 oz per quart) and applied using Foam Sprayers.

Invade Bio Cleaner and Invade Mop Clean provide solutions for cleaning organic matter with microbes that greatly improves sanitation.

If adults do not disappear within a week further treatments and inspection for other breeding sources is needed.

Use Contact Aerosols (Pyrethrins)

After breeding sources have been removed a space spray such a pyrethrins, a non residual insecticide can be applied to kill the adult flies. We also carry metered dispensers that use metered aerosols for commercial establishments.

Use Fly Lights

Another tool you can use is insect light traps, however they attract male moth flies with the greatest efficiency. Their use involved with drain flies is limited as a monitoring tool because they can't eliminate the breeding source.


Why did echolocation evolve in animals?

For dolphins and toothed whales, this technique enables them to see in muddy waters or dark ocean depths, and may even have evolved so that they can chase squid and other deep-diving species.

Echolocation allows bats to fly at night as well as in dark caves. This is a skill they probably developed so they could locate night-flying insects that birds can’t find.


Empathy Articles & More

This week Greater Good editor-in-chief Jason Marsh is reporting on highlights from the recent Being Human conference in San Francisco, including a round-up of some of the key themes and speakers, and an interview on the evolutionary roots of altruism with Yale psychologist Laurie Santos. Today, we present an interview with neuroscientist V.S. Ramachandran on mirror neurons, the subject of his Being Human talk.

Did you ever have that sensation where you’re watching someone do something—serve a tennis ball, say, or get pricked by a needle—and you can just feel exactly what they must be feeling, as if you were in their shoes?

V.S. Ramachandran

Scientists have long wondered why we get that feeling, and more than two decades ago, a team of Italian researchers thought they stumbled on an answer. While observing monkeys’ brains, they noticed that certain cells activated both when a monkey performed an action and when that monkey watched another monkey perform the same action. “Mirror neurons” were discovered.

Since that time, mirror neurons have been hailed as a cornerstone of human empathy, language, and other vital processes. But there has also been something of a mirror neuron backlash, with some scientists suggesting that the importance of mirror neurons has been exaggerated.

V.S. Ramachandran has been one of mirror neurons’ most ardent scientific champions. Ramachandran (known as “Rama” to friends and colleagues), a distinguished professor of neuroscience at the University of California, San Diego, conducted early research on mirror neurons he has since called them “the basis of civilization” in a TED talk and touted their significance in his recent book The Tell Tale Brain.

“I don’t think they’re being exaggerated,” he said a few days ago at Being Human. “I think they’re being played down, actually.”

In his presentation at Being Human, Ramachandran discussed how research on mirror neurons and “phantom limbs” suggests an extraordinary human capacity for empathy. (See this post for more details.)

After his Being Human talk, I sat down with Ramachandran to discuss what we know—and what we don’t—about these celebrated brain cells. Below is a condensed version of our conversation.

Jason Marsh: First, could you explain a little bit about what mirror neurons are and how they were discovered?

V.S. Ramachandran: Well, basically Giacomo Rizzolatti and Vittorio Gallese and some of their colleagues in Italy discovered mirror neurons. They found these neurons in the frontal lobes of the brain—the pre-frontal areas of the brain—among what were originally found as motor command neurons. These are neurons which fire when I reach out and grab a peanut, another set of neurons which fire when I reach out and pull a lever, other neurons when I’m pushing something, other neurons when I’m hitting something. These are regular motor command neurons, orchestrating a sequence of muscle twitches that allow me to reach out and grab something or do some other action.

A subset of these neurons also fire when I simply watch another person—watch you reach out and do exactly the same action. So these neurons are performing a virtual reality simulation of your mind, your brain. Therefore, they’re constructing a theory of your mind—of your intention—which is important for all kinds of social interaction.

JM: So you’ve talked about the role of mirror neurons in motor skills. I wonder if you could elaborate on the role of mirror neurons in affective experiences, in emotional experiences.

VR: Well, people have asked me that already, and I don’t know much about it. All I know is they are involved in empathy for, say, touch or a gentle caress or pain.

For example, pretend somebody pokes my left thumb with a needle. We know that the insular cortex fires cells and we experience a painful sensation. The agony of pain is probably experienced in a region called the anterior cingulate, where there are cells that respond to pain. The next stage in pain processing, we experience the agony, the painfulness, the affective quality of pain.

Ramachandran speaking at Being Human.

It turns out these anterior cingulate neurons that respond to my thumb being poked will also fire when I watch you being poked—but only a subset of them. There are non-mirror neuron pain neurons and there are mirror neuron pain neurons.

So these [mirror] neurons are probably involved in empathy for pain. If I really and truly empathize with your pain, I need to experience it myself. That’s what the mirror neurons are doing, allowing me to empathize with your pain—saying, in effect, that person is experiencing the same agony and excruciating pain as you would if somebody were to poke you with a needle directly. That’s the basis of all empathy.

JM: Just to clarify: When you talk about mirror neurons and non-mirror neurons, what percentage are you talking about?

VR: Between 10 and 20 percent [are mirror neurons]. For motor neurons, I think it’s a higher percentage—maybe about 20 percent. For sensory neurons, it’s about 10 percent. But these numbers are not all that accurate.

JM: So could you elaborate on the social implications and broader practical implications of mirror neurons?

VR: Well, [mirror neurons] enable me to see you as an intentional being, with purpose and intention. In fact, we suggested nearly a decade ago that mirror neuron dysfunction may be involved in autism. People with autism, ironically sometimes they mimic constantly what you’re doing, but it’s also true that they’re bad at imitation and they don’t have empathy, they don’t have a theory of mind, they can’t infer your intentions, they don’t engage in pretend play. In pretend play, what I do is temporarily say, “I’m going to be this superhero,” so you do role play. That requires a theory of mind.

So take all the properties of mirror neurons, make a list of them, and list all the things that are going wrong in autism—there’s a very good match. Not every symptom, but many of the symptoms match beautifully. And it’s controversial: There are about seven papers claiming that it’s true, using brain imaging, and maybe one or two claiming that there’s no correlation [between mirror neurons and autism].

JM: From your perspective, what do you think are some of the biggest misconceptions around mirror neurons—speculations that have yet to actually be validated by science?

VR: Well, I think as with any new scientific discovery, initially people are very skeptical. When people discovered that these neurons do exist, and that they exist in humans, then people went overboard and said they do everything. And I myself am partly responsible because I made this playful remark, not entirely serious, that mirror neurons will do for psychology what DNA did for biology and open up a whole new field of investigation. Turned out I was right, but it’s overdone—I mean, a lot of people, anything they can’t understand, they say it’s due to mirror neurons.


JM: And what are some of those things that people attribute to mirror neurons that we don’t yet know to be true?

VR: Well, I think my own theory about autism hasn’t been proven. It’s a plausible theory—it’s better than any other theories that are out there—but it still has not been proven. But the popular person latches onto it and says that autism’s caused by mirror neuron deficiency.

The other important thing I want to say is that mirror neurons are obviously the starting point for things like empathy, but that’s all it is—I mean, you need much more. If mirror neurons are involved in things like empathy and language and all of that, then monkeys should be very good at these things. One of the things I argue, and others have argued, is that mirror neurons are important in transmitting skills from generation to generation. I need to put myself in your shoes to observe what you’re doing, and to mime it accurately. Mirror neurons are important in that.

JM: Right, and that’s what culture’s about—the transmission of those learned skills.

VR: Exactly. That’s one of the proposals I made on the Edge website in an essay I published 10 years ago. But if that were true, it they were responsible for all that transmission of skills and culture, monkeys should be very good at those things because they have mirror neurons.

So clearly mirror neurons provide the substrate [for those skills], and maybe there are more sophisticated mirror neurons in humans than in monkeys, but they’re not by themselves [responsible].

Those kinds of errors are quite common, but that’s okay.

JM: Why do you say it’s okay?

VR: It’s how science progresses. People make overstatements, and then correct them.


Horses Need to Touch Each Other

Sense of touch is very important for horses ability to socialize and communicate with other horses in the herd,


October 3, 2012

Thomas Nagel, a professor of philosophy and of law at New York University, has made his reputation over the last fifty years as a leading contributor to moral and political philosophy, with occasional forays into the philosophy of mind. Most famously, and most relevant to his new book, Mind and Cosmos, he wrote an influential paper in the 1970s with the memorable title &ldquoWhat Is It Like to Be a Bat?&rdquo Nagel tried to demonstrate the implausibility of the notion that, even if one knew all the relevant physical facts about the brains of bats, one could have any idea what it felt like to be a bat. How could the subjective feeling of this experience be captured by a set of cold, objective biological and chemical facts about neurons? Nagel&rsquos new book revisits some of these ideas and aims to &ldquodevelop the rival alternative conceptions&rdquo to what he calls the &ldquomaterialism and Darwinism&rdquo of our age.

Mind and Cosmos
Why the Materialist Neo-Darwinian Conception of Nature Is Almost Certainly False.
By Thomas Nagel.
Buy this book.

Nagel&rsquos is the latest in what has become a small cottage industry involving a handful of prominent senior philosophers expressing skepticism about aspects of Darwin&rsquos theory of evolution by natural selection. Some, like the overtly Christian philosopher Alvin Plantinga, have made a career of dialectical ingenuity in support of the rationality of religious faith. Others, such as Jerry Fodor, are avowed atheists like Nagel, and have only tried to raise challenges to discrete aspects of evolutionary explanations for biological phenomena. Plantinga&rsquos influence has largely been limited to other religious believers, while Fodor&rsquos challenge was exposed rather quickly by philosophers as trading on confusions (even Nagel disowns it in a footnote). Nagel now enters the fray with a far-reaching broadside against Darwin and materialism worthy of the true-believing Plantinga (whom Nagel cites favorably). We suspect that philosophers&mdasheven philosophers sympathetic to some of Nagel&rsquos concerns&mdashwill be disappointed by the actual quality of the argument.

Nagel opposes two main components of the &ldquomaterialist&rdquo view inspired by Darwin&rsquos theory of evolution by natural selection. The first is what we will call theoretical reductionism, the view that there is an order of priority among the sciences, with all theories ultimately derivable from physics and all phenomena ultimately explicable in physical terms. We believe, along with most philosophers, that Nagel is right to reject theoretical reductionism, because the sciences have not progressed in a way consistent with it. We have not witnessed the reduction of psychology to biology, biology to chemistry, and chemistry to physics, but rather the proliferation of fields like neuroscience and evolutionary biology that explain psychological and biological phenomena in terms unrecognizable by physics. As the philosopher of biology Philip Kitcher pointed out some thirty years ago, even classical genetics has not been fully reduced to molecular genetics, and that reduction would have been wholly within one field. We simply do not see any serious attempts to reduce all the &ldquohigher&rdquo sciences to the laws of physics.

Yet Nagel argues in his book as if this kind of reductive materialism really were driving the scientific community. The only named target is the Nobel Prize&ndashwinning physicist Steven Weinberg, famous for his defense of the primacy of physics in such popular works as Dreams of a Final Theory (1992). Here is what Nagel writes in describing Weinberg&rsquos view:

My target is a comprehensive, speculative world picture that is reached by extrapolation from some of the discoveries of biology, chemistry, and physics&mdasha particular naturalistic Weltanschauung that postulates a hierarchical relation among the subjects of those sciences, and the completeness in principle of an explanation of everything in the universe through their unification. Such a world view is not a necessary condition of the practice of any of those sciences, and its acceptance or nonacceptance would have no effect on most scientific research.

Nagel here aligns himself, as best we can tell, with the majority view among both philosophers and practicing scientists. Just to take one obvious example, very little of the actual work in biology inspired by Darwin depends on reductive materialism of this sort evolutionary explanations do not typically appeal to Newton&rsquos laws or general relativity. Given this general consensus (the rhetoric of some popular science writing by Weinberg and others aside), it is puzzling that Nagel thinks he needs to bother attacking theoretical reductionism.

The second component of the thesis Nagel opposes is what we will call naturalism, the view that features of our world&mdashincluding &ldquoconsciousness, intentionality, meaning, purpose, thought, and value&rdquo&mdashcan ultimately be accounted for in terms of the natural processes described by the various sciences (whether or not they are ever &ldquoreduced&rdquo to physics). Nagel&rsquos arguments here are aimed at a more substantial target, although he gives us few specifics about the kind of naturalism he opposes. He does characterize it as the attempt to explain everything &ldquoat the most basic level by the physical sciences, extended to include biology,&rdquo and the one named proponent of this view is the philosopher Daniel Dennett. Although Dennett would not characterize his project as trying to explain everything at the &ldquomost basic level,&rdquo he does aim to show that phenomena such as consciousness, purpose and thought find a natural home in a picture of human beings inspired by Darwin. In the absence of any clearer statement of the argument, we will assume that this is the so-called &ldquoneo-Darwinian&rdquo picture that Nagel opposes.

Naturalists, including Dennett, defend their view by appealing to the extraordinary fruitfulness of past scientific work, including work growing out of Darwin&rsquos theory of evolution by natural selection. So what should we make of the actual work in biology that supports the &ldquomaterialist Neo-Darwinian conception of nature&rdquo that Nagel thinks &ldquois almost certainly false&rdquo? Defending such a sweeping claim might seem to require a detailed engagement with the relevant science, yet in a striking admission early on, Nagel reveals that his book &ldquois just the opinion of a layman who reads widely in the literature that explains contemporary science to the nonspecialist.&rdquo And a recurring objection to what he learned from his layman&rsquos reading of popular science writing is that much science &ldquoflies in the face of common sense,&rdquo that it is inconsistent with &ldquoevident facts about ourselves, that it &ldquorequire[s] us to deny the obvious,&rdquo and so on.

This style of argument does not, alas, have a promising history. After all, what could be more common-sensical, obvious or evident than the notion that the earth is flat and the sun revolves around the earth? All ordinary evidence supports that verdict: we know from experience that people fall off things that are spherical, especially when trying to hang upside down from them, and we know that the sun rises in the sky in one direction and sets in the other as it revolves around the seemingly flat earth. Happily, Nagel does not attempt to repudiate the Copernican revolution in astronomy, despite its hostility to common sense. But he displays none of the same humility when it comes to his preferred claims of common sense&mdashthe kind of humility that nearly 400 years of nonevident yet true scientific discoveries should engender. Are we really supposed to abandon a massively successful scientific research program because Nagel finds some scientific claims hard to square with what he thinks is obvious and &ldquoundeniable,&rdquo such as his confidence that his &ldquoclearest moral&hellipreasonings are objectively valid&rdquo?

In support of his skepticism, Nagel writes: &ldquoThe world is an astonishing place, and the idea that we have in our possession the basic tools needed to understand it is no more credible now than it was in Aristotle&rsquos day.&rdquo This seems to us perhaps the most startling sentence in all of Mind and Cosmos. Epistemic humility&mdashthe recognition that we could be wrong&mdashis a virtue in science as it is in daily life, but surely we have some reason for thinking, some four centuries after the start of the scientific revolution, that Aristotle was on the wrong track and that we are not, or at least not yet. Our reasons for thinking this are obvious and uncontroversial: mechanistic explanations and an abandonment of supernatural causality proved enormously fruitful in expanding our ability to predict and control the world around us. The fruits of the scientific revolution, though at odds with common sense, allow us to send probes to Mars and to understand why washing our hands prevents the spread of disease. We may, of course, be wrong in having abandoned teleology and the supernatural as our primary tools for understanding and explaining the natural world, but the fact that &ldquocommon sense&rdquo conflicts with a layman&rsquos reading of popular science writing is not a good reason for thinking so.

Incompatibility with common sense is not Nagel&rsquos only argument against naturalism. A second line of argument begins by appealing to what he takes to be an everyday opinion: that there are objective moral, logical and mathematical truths. He then argues that the existence of these kinds of objective truths is incompatible with naturalism. For the moral case, Nagel asks: If our moral faculties are simply the result of evolution, how can they be reliable measures of objective moral truth? Why should evolution prefer the perception of moral truth to whatever happens to be advantageous for reproduction? Thus, if some of our moral beliefs really are objectively true, then they cannot be the result of evolution. And because he is confident that we do know some objective moral truths, Nagel concludes that &ldquoa Darwinian account of the motives underlying moral judgment must be false, in spite of the scientific consensus in its favor.&rdquo Recognizing that readers will find this inference jarring, Nagel adds: &ldquoI, even more strangely, am relying on a philosophical claim to refute a scientific theory supported by empirical evidence.&rdquo

There is, indeed, much that is strange here. To begin, there is nothing remotely common-sensical about Nagel&rsquos confidence in the objectivity of moral truth. While Nagel and his compatriots apparently take very seriously their moral opinions&mdashso seriously that they find it incredible to suggest that their &ldquoconfidence in the objective truth of [their] moral beliefs&rdquo might, in fact, be &ldquocompletely illusory&rdquo&mdashthis can hardly claim the mantle of &ldquothe common sense view.&rdquo Ordinary opinion sometimes tends toward objectivism, to be sure&mdashoften by relying on religious assumptions that Nagel explicitly rejects&mdashbut it also often veers toward social or cultural relativism about morality. Whether morality is truly objective is a philosopher&rsquos claim (and a controversial one even among philosophers) about which &ldquocommon sense&rdquo is either agnostic or mixed.

We take no stance on Nagel&rsquos hypothesis that if our moral faculties are simply the result of evolution, they cannot be reliable measures of objective moral truth. But we should note that Nagel&rsquos colleague, philosopher Sharon Street, accepts it and draws the opposite conclusion. She argues that because this hypothesis is true, and because we are obviously the products of evolution, we should give up the idea that there are objective moral truths in Nagel&rsquos sense. Given the philosophical plausibility of Street&rsquos alternative response&mdashnot to mention the simplistic evolutionary reasoning the whole debate is predicated on&mdashit is hard to see why any biologist should be given pause by Nagel&rsquos argument.

A more interesting challenge&mdashreally, the only interesting philosophical point raised in the book&mdashconcerns logical and mathematical truths. Is it possible, Nagel asks, to reconcile a naturalistic and biological picture of the evolution of our cognitive capacities with the confidence we have in our ability to do logic and mathematics? Nagel&rsquos argument invokes a contrast with our perceptual capabilities, because our ability to reliably perceive many of the features of our physical environment seems likely to have an evolutionary explanation. (After all, if we could not reliably spot sudden cliffs or saber-toothed tigers, our reproductive fitness would be seriously compromised!) But logical truths are not like that, Nagel argues. It is self-evident that something cannot be both red and not-red at the same time (the &ldquolaw of non-contradiction&rdquo). So, too, it is self-evident that if all men are mortal, and Socrates is a man, then Socates is necessarily mortal. Even if evolution endowed us with the capacity to recognize the law of non-contradiction and to draw valid deductive inferences, how does it explain the obvious truth of these logical claims? Nagel&rsquos response to this question is that evolution cannot&mdashand the problem is even worse than that:

Any evolutionary account of the place of reason presupposes reason&rsquos validity and cannot confirm it without circularity.

Eventually the attempt to understand oneself in evolutionary, naturalistic terms must bottom out in something that is grasped as valid in itself&mdashsomething without which the evolutionary understanding would not be possible.

In other words, even if one thinks there is an evolutionary explanation for why we recognize the obviousness of logical, mathematical and scientific truths, there would still be the question of why we think evolutionary theory itself is justified. An evolutionary explanation of that latter fact would have to presuppose the correctness of the theory whose justification we are questioning, making the argument circular: we would have to assume that evolutionary theory is true in order to investigate whether it is true!

There is a response to this kind of challenge, one that is widely embraced by philosophical naturalists (though, again, not mentioned by Nagel). This response starts by noting that we determine what is &ldquorational&rdquo or &ldquojustified&rdquo simply by appealing to the most successful forms of inquiry into the world that human beings have developed. Paradigmatic examples of those successful forms of inquiry are, of course, physics, chemistry and biology. They are successful precisely in the way that Aristotelian science was not: they enable us to navigate the world around us, to predict its happenings and control some of them. To confuse one&rsquos intuitive confidence in the logical and epistemic norms that make these sciences possible with some kind of a priori access to the &ldquorational order of the world,&rdquo as Nagel puts it, is to forget whence that confidence derives&mdashnamely, the very success of these sciences. For philosophical naturalists, the charge of circularity is empty, akin to suggesting that the need for a usable table to have legs requires some justification beyond the fact that the legs actually do a necessary job.

Philosophical naturalists often appeal to the metaphor of &ldquoNeurath&rsquos Boat,&rdquo named after the philosopher who developed it. Our situation as inquirers trying to understand the world around us, according to Neurath, is like that of sailors who must rebuild their ship while at sea. These sailors do not have the option of abandoning the ship and rebuilding a new one from scratch. They must, instead, try to rebuild it piecemeal, all the time staying afloat on other parts of the ship on which they continue to depend. In epistemological terms, we are also &ldquoat sea&rdquo: we cannot abandon all the knowledge about the world we have acquired from the sciences and then ask what we really know or what is really rational. The sciences that have worked so well for us are precisely our benchmark for what we know and what is rational they&rsquore the things that are keeping us &ldquoafloat.&rdquo Extending this metaphor, we can say that Nagel is the sailor who says, &ldquoI know the ideal form a ship should take&mdashit is intuitively obvious, I am confident in it&mdashso let us jump into the ocean and start building it from scratch.&rdquo

We agree with Nagel that if the sciences could not explain our capacity to have thoughts about the world around us, that would be a serious failing and a reason to call their findings into question. But they can and they do! It is here that Nagel&rsquos lack of engagement with contemporary cognitive science and his idiosyncratic views about what a scientific explanation should look like make his argument especially perplexing. He writes, in what might seem a massive concession to his naturalistic opponents, &ldquoThe appearance of animal consciousness is evidently the result of biological evolution, but this well-supported empirical fact is not yet an explanation&mdashit does not provide understanding, or enable us to see why the result was to be expected or how it came about.&rdquo On Nagel&rsquos view, consciousness arose from evolution, but despite knowing this fact, we have not explained the origin of consciousness. In a similar vein, Nagel writes:

It is not an explanation to say just that the physical process of evolution has resulted in creatures with eyes, ears, central nervous systems, and so forth, and that it is simply a brute fact of nature that such creatures are conscious in the familiar ways. Merely to identify a cause is not to provide a significant explanation, without some understanding of why the cause produces the effect.

Nagel endorses the idea that explanation and prediction are symmetrical: &ldquoAn explanation must show why it was likely that an event of that type occurred.&rdquo In other words, to explain something is to be in a position to have predicted it if we could go back in time. He also writes, &ldquoTo explain consciousness, a physical evolutionary history would have to show why it was likely that organisms of the kind that have consciousness would arise.&rdquo Indeed, he goes further, claiming that &ldquothe propensity for the development of organisms with a subjective point of view must have been there from the beginning.&rdquo

This idea, however, is inconsistent with the most plausible views about prediction and explanation, in both philosophy and science. Philosophers of science have long argued that explanation and prediction cannot be fully symmetrical, given the importance of probabilities in explaining natural phenomena. Moreover, we are often in a position to understand the causes of an event, but without knowing enough detail to have predicted it. For example, approximately 1 percent of children born to women over 40 have Down syndrome. This fact is a perfectly adequate explanation of why a particular child has Down syndrome, but it does not mean we could have predicted that this particular child would develop it. Causes alone are frequently deemed sufficient to explain events knowing enough to predict those events in advance is an important scientific achievement, but not essential to explanation.

Nagel doesn&rsquot think so, and because of that, he advocates the reintroduction of teleological reasoning into science. (Teleology&mdashthe idea that natural phenomena have built-in purposes or ends&mdashwas central to Aristotelian science, and it remained very influential until the scientific revolution.) In his discussion of the origin of life, Nagel says that natural teleology would mean that, &ldquoin addition to physical law of the familiar kind, there are other laws of nature that are &lsquobiased toward the marvelous.&rsquo&rdquo

This is an astonishing though certainly evocative phrase (Nagel adapts it from another writer), yet Nagel offers no further explication of it. He does admit that this proposal &ldquoflies in the teeth of the authoritative form of explanation that has defined science since the revolution of the seventeenth century.&rdquo Unfortunately, he is also extremely unclear about what he means by &ldquonatural teleology,&rdquo other than assuring the reader that it is neither part of standard physical laws nor the introduction of theology. One might think that &ldquoprinciples of self-organization or of the development of complexity over time,&rdquo which Nagel gives as examples of natural teleology, are the sort of things studied by mainstream protein chemists, developmental biologists and condensed-matter physicists. But apparently these sciences, which study how complex order can be built up from simple physical processes, are not on the right track. Nagel never explains why.

We conclude with a comment about truth in advertising. Nagel&rsquos arguments against reductionism are quixotic, and his arguments against naturalism are unconvincing. He aspires to develop &ldquorival alternative conceptions&rdquo to what he calls the materialist neo-Darwinian worldview, yet he never clearly articulates this rival conception, nor does he give us any reason to think that &ldquothe present right-thinking consensus will come to seem laughable in a generation or two.&rdquo Mind and Cosmos is certainly an apt title for Nagel&rsquos philosophical meditations, but his subtitle&mdash&rdquoWhy the Materialist Neo-Darwinian Conception of Nature Is Almost Certainly False&rdquo&mdashis highly misleading. Nagel, by his own admission, relies only on popular science writing and brings to bear idiosyncratic and often outdated views about a whole host of issues, from the objectivity of moral truth to the nature of explanation. No one could possibly think he has shown that a massively successful scientific research program like the one inspired by Darwin&rsquos theory of evolution by natural selection &ldquois almost certainly false.&rdquo The subtitle seems intended to market the book to evolution deniers, intelligent-design acolytes, religious fanatics and others who are not really interested in the substantive scientific and philosophical issues. Even a philosopher sympathetic to Nagel&rsquos worries about the naturalistic worldview would not claim this volume comes close to living up to that subtitle. Its only effect will be to make the book an instrument of mischief.

Why has natural selection always been the most contested part of evolutionary theory? asks Jeffrey A. Coyne in &ldquoThe Improbability Pump&rdquo (May 10, 2010), reviewing The Greatest Show on Earth, by Richard Dawkins, and Jerry Fodor and Massimo Piattelli-Palmarini&rsquos What Darwin Got Wrong.

Brian Leiter Brian Leiter is the Karl N. Llewellyn Professor of Jurisprudence and director of the Center for Law, Philosophy and Human Values at the University of Chicago.

Michael Weisberg Michael Weisberg is an associate professor of philosophy at the University of Pennsylvania, where he is also a faculty affiliate of the Institute for Research in Cognitive Science.



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