The identity theory of mind holds that states and processes of the mind are identical to states and processes of the brain. Strictly speaking, it need not hold that the mind is identical to the brain. Idiomatically we do use ‘She has a good mind’ and ‘She has a good brain’ interchangeably but we would hardly say ‘Her mind weighs fifty ounces’. Here I take identifying mind and brain as being a matter of identifying processes and perhaps states of the mind and brain. Consider an experience of pain, or of seeing something, or of having a mental image. The identity theory of mind is to the effect that these experiences just are brain processes, not merely correlated with brain processes.
Some philosophers hold that though experiences are brain processes they nevertheless have fundamentally non-physical, psychical, properties, sometimes called ‘qualia’. Here I shall take the identity theory as denying the existence of such irreducible non-physical properties. Some identity theorists give a behaviouristic analysis of mental states, such as This is great: take this nifty series of listening tests and in 15 minutes you objectively find out how acute your sense of pitch is. The third test determines if you have a weak sense of rhythm, which is known to be linked with bad dancing. (No word on whether this is "objectively" connected with success in one's social life, or lack thereof. And when a computer starts criticizing your social life...)
I scored a 66.7 on the first test, the one on tone deafness, which was pretty much average. Then I got a 4.8 on the pitch accuracy test -- that means that at 500Hz (near the B below the C above middle C), I can discern two tones that are 4.8Hz apart. (Half tones are about 29Hz apart at that pitch, so this is a small but appreciable gap.) Interesting to see that the 6Hz tones sound very different to me, while the 3Hz tones sound almost exactly the same. That placed me at only the 13th percentile. I blame my poor relative performance on the probability that this online quiz is overrun with musical geniuses -- they wrecked the curve!
Having realized long ago that I didn't have a great ear (my high school chorus teacher can attest to this), I took this as no great surprise. That's fine, I thought -- I'll really shine in the rhythm section. But it was not to be. I scored a 68%, placing me at the 31st percentile.
Despite my vaguely depressing results, I really like these tests. It's fascinating that you can sit down and in 15 minutes find out something about how your ear and brain work. Also interesting to think that people can have such different experiences of similar stimuli. Auditory acuity is largely a natural, unchangeable characteristic of a person (at least an adult). Not to get too Brave New World, but I wonder if it could actually be helpful to test people's hearing to see how well they can, say, learn to play the violin. Maybe if my chorus teacher knew about my tin ear, she would have been a little more understanding of my flat singing -- or maybe she never would've let my hopeless self even in the doorway.
As fast and powerful as these listening tests are, they can't quite match color blindness tests. I remember sitting down for my first such test in elementary school, and about a minute in, the nurse pretty much knew: my red cones are a bit strange.
Permalink – Posted by Amos Kenigsberg – Posted under Mind & Brain – At 2007-01-24 05:35
Ins & Outs of Vulcan Charity
In 2000, University of Chicago behavioral economist Richard Thaler trumpeted that economics was finally moving "From Homo Economicus to Homo Sapiens"—that is, dropping the outdated assumption that people are robo-beings who always know what exactly they want and pursue those desires perfectly rationally (think Spock from Star Trek). Six years later, even after psychologist and outsider Daniel Kahneman stumbled the field of economics and walked off with their Nobel Prize, much of the field continues to go on ahead as if the psychologists had never kicked over one of their central pillars. (Thaler, who's next in line to win a Nobel for behavioral economics, actually realized his optimism was misplaced, pointing out several reasons why psychological factors will "trap me into thinking that other economists will agree with me—20 years of contrary evidence notwithstanding.")
Tim Harford's recent article claiming that people are not really being altruistic when they give to charity relies heavily on this antediluvian thinking. For example, he says that anybody that gives money to charity should give it all to the one project that they think would do the most good, because if it does the most good with your first dollar, it'll do the most good with your second, and your third, and so on (as long as you're not actually giving a Gates-ian amount that could actually end the problem entirely). And because most people don't donate this way, they must not really care about their donations actually doing good, he says. This of course ignores the fact that giving money is not only a transfer of funds but also a statement of support, one that is understood by the giver, the receiver, and everyone else, seemingly, that's not practicing narrow-minded economics. And even if we accept that one-cause giving is the most rationally effective way to give, it's plainly obvious that people very often do not maximize economic effectiveness—even when it would be to their own advantage. That's the whole point of behavioral economics! The well-documented 35-year history of these ideas seems to have sailed right by without troubling Harford's analysis a bit.
He also says people should almost never do charitable volunteer work but instead just work more and use the money to hire people for do-gooder work. "A Dutch banker can pay for a lot of soup-kitchen chefs and servers with a couple of hours' worth of his salary, but that wouldn't provide the same feel-good buzz as ladling out stew himself, would it?" Harford's off-hand coarseness reflects well how pre-behavioral economics misses the human dimension of humans. Mightn't the folks eating at the soup kitchen be happy that professional people are volunteering to help in addition to people who are professional helpers? Couldn't the banker be affected by her experience at the soup kitchen and donate money to a political campaign that eventually had even greater power to improve the lot of poor people?
But if you're hoping to find a piece on the economics of Vulcan charity, look no further.
Permalink – Posted by Amos Kenigsberg – Posted under Mind & Brain – At 2006-10-16 14:00
Sex Hormones in the Brain: Wimps Rejoice
For those out there who dream of being a little more manly, be careful what you wish for. A new Yale study reports that excessive testosterone kills brain cells. Neurons in lab dishes treated with large doses of the hormone for just a few hours began committing the cellular suicide known as apoptosis. The study used concentrations higher than those normally found in the body, but steroid abuse is known to increase testosterone to dangerous levels. Neuronal death may explain the behavioral changes seen in some steroid users. As one author puts it:
Next time a muscle-bound guy in a sports car cuts you off on the highway, don't get mad -- just take a deep breath and realize that it might not be his fault.
(Honestly, I always suspected that certain drivers’ noggins were full of kamikaze brain cells.)
Just in case women weren’t feeling smug enough reading this, the researchers ran a similar trial with estrogen and discovered that it may be “neuroprotective,” resulting in less cell death. And another recent study found that treatment with progesterone—a hormone involved in the menstrual cycle—improves survival among brain injury victims. So for gals who have bemoaned our wildly fluctuating female hormones since puberty, take heart: they may wreak havoc with our bodies, but they do a brain good.
Late-breaking addition: Check out these Data articles on the relationship between testicle size and brain size in bats and the toxicity of testosterone.
Permalink – Posted by Jennifer Barone – Posted under Mind & Brain – At 2006-10-05 19:00
Don't Put People in a Box
The latest installment of Horganism looks at an IEEE Spectrum article about Simon Baron-Cohen's theory about how autistic people are "merely the extreme of a continuum on which all of us reside. In this view, autism is a difference not in kind of thinking, but in degree." The trait he's talking about is "systemizing," or how much a person focuses on "those aspects of the world that form regular, repeatable, law-governed patterns"—like watching Wapner at the same time every day and freaking out if that doesn't happen. Autistics are extreme systemizers, he says, and autism is more common among men because they are more systemizing than women, on the whole.
I think Baron-Cohen's emphasis on a gradual spectrum of systemizing is smart, but I also share Horgan's general skepticism about big claims on human genetics. And when you get to the second page of the Spectrum article, you can see where Baron-Cohen has stumbled into the stereotyping-humans pitfall, and is now hurtling toward the sharpened wooden sticks of truth (a punishment that might be levied by Borat, who's played by Sacha Baron-Cohen, Simon's cousin). He says that since men are on average more systemize-aphilic (not -phallic, mind you) that means that autism represents "the extreme male mind." This is not just a throwaway quote; on page one of his book The Essential Difference, Baron-Cohen writes, "The female brain is predominantly hard-wired for empathy. The male brain is predominantly hard-wired for understanding and building systems."
Let's look at an elucidating comparison. It's well known that men are, on average, taller than women. Does that mean that the five-foot-eleven-inch Famke Janssen (where she's from they call it 180 centimeters) represents "the extreme male body"? And Danny DeVito, barely five feet with his fancy Italian shoes on, represents "the extreme female body"? (For extreme systemizers who don't notice such gossippy, plebeian details, the answer is no.)
The problem with Baron-Cohen's reasoning is that he's taken one trait that differs between two groups and started talking like—and seemingly believing that—the trait is what defines the difference between two groups. But just as there's more to physical sex differences than height, there's also more to mental sex differences than systemizing. I think this kind of slip-up is all too common among people who are convinced that genes and/or sex is destiny and are always looking for the nut (pun intended) of the difference between men and women. In fact, another camp of Men-Are-From-Mars-type scientists insists that the real difference between men and women is that men are more aggressive. So which is it?
Logic demands that these camps can't both be right about la difference—and in fact neither one is. There are natural mental distinctions between men and women, but they are complicated, subtle, and varied. Anyone who sums up the differences in one neat sentence is over-simplifying—but it does make a good story, don't it?
Permalink – Posted by Amos Kenigsberg – Posted under Mind & Brain – At 2006-10-04 19:00
Money
Does Buy You Happiness. Maybe.
People have been probably been wondering if money brings happiness ever since Croesus, a king in what is today Turkey, had a mixture of silver and gold pounded into bean-shaped ingots 4,000 years ago. Only over the past few years has the subject become a scientific hot topic. And the results, as far as I can tell, are... (drum roll)... somewhat muddled. One argument that has gained considerable prominence recently is that more money does make you significantly happier if you're living in poverty, barely squeaking by, but additional income past that has negligible happiness benefits.
Not so, says a new study that tracked ten thousand British people over the course of several years and focused especially on 116 who won big lottery payouts (over 1,000 pounds; mean of 4,300 pounds) during that time. One strength of the study is that it followed the winners themselves for two years after they won and also included data on the same people from the two years before the wheel of Fortuna rolled their way; the researchers may have avoided confounding factors that needle at other studies, such as those that compare people at different income levels (happiness might affect income), those that look at people who are given raises (change in status along with change in income), etc.
The study finds that big pay-offs increase people's happiness by an average of 1.4 points on a 36-point scale, as measured by a standard questionnaire. By comparison, the most dramatic effect on someone's happiness is being widowed, which on average produces a 5-point drop. Whether being widowed is 3.5 times more intense than winning the lottery -- and therefore worth negative 15,000 pounds -- is a question only an economist would address. (And the bonus is in no way enough to justify Terrell Owens' heartless publicist saying he had "25 million reasons why he should be alive," referring to his contract.)
Lest we think this ends the debate, there are some mysterioso findings in there, too:
- Lottery wins yield these happiness benefits only 2 years after the windfall. In the same year that people win, their happiness actually decreases by .6 points. The dreaded grabby-brother-in-law effect?
- High-income people got twice as many happy points from winning as did low-income people! Maybe that's why they work high-income jobs.
- Big winners gained .7 happy points the year before they won. One wonders if this is a statistical fluke, but does that raise a red flag?
As a big believer in behavioral economics, I wonder if the effects have more to do with human idiosyncracies than the actual amount of money that is objectively gained. Is it possible that the happiness gains are due not to having more money but to the feeling of being someone who won money -- someone that God and/or luck is smiling upon?
(Thanks to AB for the tip.)
Permalink – Posted by Amos Kenigsberg – Posted under Mind & Brain – At 2006-09-28 19:00
Eating Helmets
The University of Bath put out a press release about some research suggesting that motorists leave less berth for cyclists with helmets than those without, which presumably increases the chances of a crash. "This study suggests wearing a helmet might make a collision more likely in the first place," says the researcher, traffic psychologist Ian Walker, who was in two crashes while doing the research, both during the half when he was wearing a helmet. Helmet boosters didn't like these dirty lies from Bath, and predictably -- perhaps accurately -- said the things are still worth it.
As for why drivers give the helmeted less room, Walker says it's because they think bicyclists wearing helmets are more experienced, skilled, and predictable, so they can get closer without hitting them. At the risk of crossing a real traffic psychologist (I've heard they can trick people into driving into trees), I'd suggest a different explanation: drivers are consuming the safety that bicyclists gain by wearing helmets. I.e., they feel that the bicyclists with helmets are relatively safe in the event of an accident, so they don't need to worry much about hitting them.
This "risk compensation" is often seen in people who get access to new safety measures and then start doing more dangerous things, e.g., better skydiving gear -> more dangerous dives, seat belts -> more dangerous driving, better AIDS drugs -> more unsafe sex, sunscreen -> more sun exposure and potentially more skin cancer, etc. The bicycle example is a little different in that in the other cases, people "consume" their own safety benefits, whereas motorists are consuming someone else's increased safety -- a rare case of risk compensation/moral hazard. (Which is particularly galling considering that decent road bicyclists only need helmets to protect themselves from cars.) Of course, judging by how people sometimes change when they get into a driver's seat, it might not be that surprising.
Permalink – Posted by Amos Kenigsberg – Posted under Mind & Brain – At 2006-09-14 19:00
Your Hygienic Conscience
The NY Times has a story on a really fascinating finding: People who are feeling guilty have an increased desire to literally wash their hands, presumably to figuratively wash their hands of their wrongdoing.
The researchers had one group of students recall an unethical act from their past, like betraying a friend, and another group reflect on an ethical deed, like returning lost money. Afterward, the students had their choice of a gift, either a pencil or an antiseptic wipe. Those who had reflected on a shameful act were twice as likely as the others to take the wipe.
Very interesting to consider how the washing-your-hands metaphor ties in with an underlying human mechanism for purging guilt. I suspect that some ritualized types of guilt dumping (like this metaphorical type) are also instinctual. Is confession (either lay or religious) a natural way to clear your conscience? And what about the eating -- e.g., taking the Eucharist or, say, inhaling a pint of Ben and Jerry's?
t perhaps more importantly, did the researchers feel guilty for holding a study where the prizes were a pencil or an antiseptic wipe? Thanks a lot, doc. (Thanks to EZ for the tip.)
In philosophy, supervenience is a kind of dependency relationship, typically held to obtain between sets of properties. According to one standard definition, a set of properties A supervenes on a set of properties B, if and only if any two objects x and y which share all properties in B (are "B-indiscernible") must also share all properties in A (are "A-indiscernible"). That is, A-properties supervene on B-properties if being B-indiscernible implies being A-indiscernible. The properties in B are called the base properties (or sometimes subjacent or subvenient properties), and the properties in A are called the supervenient properties. Equivalently, if two things differ in their supervenient properties then they must differ in their base properties. To give a somewhat simplified example, if psychological properties supervene on physical properties, then any two persons who are physically indistinguishable must also be psychologically indistinguishable; or equivalently, any two persons who are psychologically different (e.g., having different thoughts), must be physically different as well. Importantly, the reverse does not follow (supervenience is not symmetric): even if being the same physically implies being the same psychologically, two persons can be the same psychologically yet different physically: that is, psychological properties are multiply realized in physical properties.
Supervenience has traditionally been used to describe relationships between sets of properties in a manner which does not imply a strong reductive relationship.[1] For example, many hold that economic properties supervene on physical properties, in that if two worlds were exactly the same physically, they would also be the same economically. However, this does not entail that economics can be reduced in any straightforward way to physics. Thus, supervenience allows one to hold that "high-level phenonema" (like those of economics, psychology, or aesthetics) depend, ultimately, on physics, without assuming that one can study those high-level phenomena using means appropriate to physics.
Contents [hide]
1 History
2 Definitions
3 Varieties of supervenience
4 Examples of supervenient properties
4.1 Value properties
4.2 Mental properties
4.3 Computational properties
5 Arguments against supervenience-based formulations of physicalism
5.1 Epiphenomenal ectoplasm
5.2 The lone ammonium molecule problem
5.3 Modal status problem
5.4 Problem of necessary beings
6 Notes
7 See also
8 External links
[edit] History
Donald Davidson popularized the use of supervenience in the philosophy of mind.Supervenience, which means literally "coming or occurring as something novel, additional, or unexpected" [1], from "super," meaning on, above or, additional, and "venire," meaning to come, shows occurrences in the Oxford English Dictionary dating back to 1644.
Its systematic use in philosophy is considered to have begun in early 20th-century metaethics and emergentism. As G.E. Moore wrote in 1922, "If a given thing possesses any kind of intrinsic value in a certain degree, then... anything exactly like it, must, under all circumstances, possess it in exactly the same degree" (as cited in [1]). The usage also carried over into the work R. M. Hare. For discussion of the emergentist roots of supervenience see http://plato.stanford.edu/entries/supervenience/#2.2.
In the 1970s Donald Davidson was the first to use the term to describe a broadly physicalist (and non-reductive) approach to the philosophy of mind. As he said in 1970, "supervenience might be taken to mean that there cannot be two events alike in all physical respects but differing in some mental respects, or that an object cannot alter in some mental respects without altering in some physical respects." [2]
In subsequent years Terry Horgan, David Lewis, and especially Jaegwon Kim formalized the concept and began applying it to numerous issues in the philosophy of mind. This raised numerous questions about how various formulations relate to one another, how adequate the formulation is to various philosophical tasks (in particular, the task of formulating physicalism), and whether it avoids or entails reductionism.
[edit] Definitions
In the contemporary literature, there are two primary (and non-equivalent) formulations of supervenience:
A-properties supervene on B-properties if and only if all things that are B-indiscernible are A-indiscernible. Formally:
A-properties supervene on B-properties if and only if anything that has an A-property has some B-property such that anything that has that B-property also has that A-property. Formally:
For example, if one lets A be a set of mental properties, B be a set of physical properties, and chooses a domain of discourse consisting of persons, then (1) says that any two persons who are physically indiscernible are mentally indiscernible, and (2) says that any person who has a mental property has some physical property such that any person with that physical property has that mental property.
Some points of clarification. First, the definitions above involve quantification over properties and hence higher order logic. Second, in (1), expressions of the form capture the concept of sharing all properties, or being indiscernible with respect to a type of property. Thus, (1) can be understood more intuitively as the claim that all objects that are indiscernible with respect to a base set of properties are indiscernibile with respect to a supervenient set of properties, or, as it is also sometimes said, that B-twins are A-twins. Finally, supervenience claims typically involve some modal force, however, the way that modal force is specified depends on which more specific variety of supervenience one decides upon (see below).
(1) and (2) are sometimes called "schemata", because they do not correspond to actual supervenience relations until the sets of properties A and B, the domain of entities to which those properties apply, and a modal force have been specified. For modal forms of supervenience, the modal strength of the relation is usually taken to be a parameter (that is, the possible worlds appealed to may be physically possible, logically possible, etc.). Also, note that in the early literature properties were not always central, and there remain some who prefer to frame the relation in terms of predicates, facts, or entities instead, for example.
[edit] Varieties of supervenience
There are many varieties of supervenience proposed in the philosophical literature, thanks in part to what David Lewis called the "unlovely proliferation"[3] which occurred beginning in the 1980s, inspired largely by Jaegwon Kim's work. These varieties are based both on (1) and (2) above, but since (1) is more common we shall focus on varieties of supervenience based on it.
We can begin by distinguishing between local and global supervenience:
Local: For any two objects x and y, if x and y are base-indiscernible, they are supervenient-indiscernible.
For example, if mental states locally supervene on brain states, then being in the same brain state entails being in the same mental state.
Global: For any two worlds w1 and w2, if w1 and w2 are base-indiscernible, they are supervenient-indiscernible.
For example, if psychological properties globally supervene on physical properties, then any two worlds physically the same will be psychologically the same. The value of global supervenience is that it allows for supervenient properties to be determined not by local properties of an individual thing alone, but by some wider spatiotemporal distribution of things and properties. For example, something's being a dollar bill depends not only on the paper and the inks it is made out of, but also on a widely dispersed variety of features of the world it occupies.
Both local and global supervenience come in many forms. Local supervenience comes in strong and weak varieties:
Weak: For any world w, and for any two objects x in w and y in w, if x and y are base-indiscernible, they are supervenient-indiscernible.
Strong: For any worlds w1 and w2, and for any two objects x in w1 and y in w2, if x and y are base-indiscernible, they are supervenient-indiscernible.
The difference is essentially whether correlations between base and supervenient properties hold within worlds only, or across possible worlds. For example, if psychological properties strongly locally supervene on physical properties, then any two people physically the same, in any two worlds, will also be psychologically the same. On the other hand, if psychological properties only weakly locally supervene on physical properties, then those correlations between base and supervenient properties that hold in virtue of the supervenience relation are maintained within each world, but can be different in different worlds. For example, my physical duplicates in the actual world will have the same thoughts as I have; but my physical duplicates in other possible worlds may have different thoughts than I have in the actual world.
There are also several kinds of global supervenience relations, which were introduced to handle cases in which worlds are the same at the base level and also at the supervenient level, but where the ways the properties are connected and distributed in the worlds differ. For example, it is consistent with global mental–physical supervenience on the simple formulation described above for two worlds to have the same number of people in the same physical states, but for the mental states to be distributed over those people in different ways (e.g. my father has my thoughts in the other world, and he has my thoughts). To handle this, property-preserving isomorphisms (1-1 and onto functions between the objects of two worlds, whereby an object in one world has a property if and only if the object which that function takes you to in the other world does) are used, and once this is done, several varieties of global supervenience can be defined.
Other varieties of supervenience include multiple-domains supervenience and similarity-based supervenience.
[edit] Examples of supervenient properties
[edit] Value properties
The value of a physical object to an agent is sometimes held to be supervenient upon the physical properties of the object. In aesthetics, the beauty of La Grande Jatte might supervene on the physical composition of the painting (the specific molecules that make up the painting), the artistic composition of the painting (in this case, dots), the figures and forms of the painted image, or the painted canvas as a whole. In ethics, the goodness of an act of charity might supervene on the physical properties of the agent, the mental state of the agent (his or her intention), or the external state of affairs itself. Similarly, the overall suffering caused by an earthquake might supervene on the spatio-temporal entities that constituted it, the deaths it caused, or the natural disaster itself.
[edit] Mental properties
In philosophy of mind, many philosophers make the general claim that the mental supervenes on the physical. In its most recent form this position derives from the work of Donald Davidson, although in more rudimentary forms it had been advanced earlier by others. The claim can be taken in several senses, perhaps most simply in the sense that the mental properties of a person are supervenient on their physical properties. Then:
If two persons are indistinguishable in all of their physical properties, they must also be indistinguishable in all of their mental properties.
An alternative claim, advanced especially by John Haugeland, is a kind of weak local supervenience claim; or, weaker still, mere global supervenience. The claim that mental properties supervene globally on physical properties requires only a quite modest commitment: any difference between two possible worlds with respect to their instantiated mental properties entails at least some difference in the physical properties instantiated in those two worlds. Importantly, it does not require that the mental properties of an individual person supervene only on that person's physical state.
This weak global thesis is particularly important in the light of direct reference theories, and semantic externalism with regard to the content both of words and (more relevant to our concerns here) of thoughts. Imagine two persons who are indistinguishable in their local physical properties. One has a dog in front of his eyes and the other has a dog-image artificially projected onto his retinae. It might be reasonable to say that the former is in the mental state of seeing a dog (and of knowing that he does so), whereas the latter is not in such a state of seeing a dog (but falsely believes that he sees one).
There is also discussion among philosophers about mental supervenience and our experience of duration. If all mental properties supervene only upon some physical properties at durationless moments, then it may be difficult to explain our experience of duration. The philosophical belief that mental and physical events exist at a series of durationless moments that lie between the physical past and the physical future is known as presentism, and is a form of belief in Galilean relativity.
[edit] Computational properties
There are several applications of the theory of supervenience to be found in computer networking. For example, in a dial-up internet connection, the audio signal on a phone line transports IP packets between the user's computer and the Internet service provider's computer. In this case, the arrangement of bytes in that packet supervenes on the physical properties of the phone signal. More generally, each layer of the OSI Model of computer networking supervenes on the layers below it.
These computer examples illustrate a general principle: we can find supervenience wherever a message is conveyed by a representational medium. When we see a letter "a" in a page of print, for example, the meaning latin lowercase "a" supervenes on the geometry of the boundary of the printed glyph, which in turn supervenes on the ink deposition on the paper.
[edit] Arguments against supervenience-based formulations of physicalism
Although supervenience seems to be perfectly suited to explain the predictions of physicalism (i.e. the mental is dependent on the physical), there are four main problems with it. They are Ephiphenomenal ectoplasm, the lone ammonium molecule problem, modal status problem and the problem of necessary beings.
[edit] Epiphenomenal ectoplasm
Epiphenomenal ectoplasm was proposed by Horgan and Lewis in 1983, in which they stated, a possible world (a world that could possibly exist) W is identical to our world in the distribution of all mental and physical characteristics (i.e. they are identical), except world W contains an experience called epiphenomenal ectoplasm that does not causally interact with that world. If supervenience physicalism is true, then such a world could not exist because a physical duplicate of the actual world (the world that is known to exist) could not possess an epiphenomenal ectoplasm. This was rectified by Frank Jackson, by adjusting the application of supervenience within physicalism to state "Physicalism is true at a possible world W if and only if any world which is a minimal physical duplicate (i.e. identical) of W is a duplicate of W simpliciter."
[edit] The lone ammonium molecule problem
The lone ammonium molecule problem provides a problem for Jackson's solution to epiphenomenal ectoplasm. It was proposed by Jaegwon Kim in 1993 when he stated that according to Jackson's idea of supervenience, a possible world W was identical to the actual world, except it possessed an extra ammonium molecule on one of Saturn’s rings. This may not seem to provide much of a problem, but because Jackson's solution refers only to minimal physical duplicates, this allows for the mental properties of W to be vastly different than in the actual world. If such a difference would cause mental differences on Earth, it would not prove our misunderstanding of physicalism.
[edit] Modal status problem
The modal status problem is only problematic if one thinks of physicalism as a contingent truth (i.e. not necessary), because it is described in terms of modal notions (i.e. through modal realism). The problem is presented when from the statement "Minimal physical truths entail all truths", one derives the statement "S (a statement that describes all minimal physical truths) entails S* (a statement that describes the world)". This statement is a necessary truth, and therefore supervenience physicalism could not be contingent. The solution to this is to accept the above statement not as the equivalent of physicalism, but as an entailment of it.
[edit] Problem of necessary beings
The problem of necessary beings was proposed by Jackson in 1998, in which he stated that a necessary being exists in all possible worlds as a non-physical entity, and therefore proves physicalism false. However, physicalism allows for the existence of necessary beings, because any minimal physical duplicate would have the same mental properties as the actual world. This however is paradoxical, based on the fact that physicalism both permits and prevents the existence of such beings. However, the existence of necessary beings is paradoxical in itself. They are both distinct from the physical world and dependent upon it. This violates Hume's fork which states, "there are no necessary connections between distinct existences".