Supervenience
Encyclopedia
In philosophy
, supervenience is a kind of dependency relationship. For example, mental states might depend on physical brain states. This dependency is typically held to obtain between sets of properties
. A classic example (which is not supported by scientific evidence) is that mental states of pain
supervene on 'C-fibers firing'
. According to one standard definition, a set of properties A (pain) supervenes on a set of properties B (brain), 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"). In our example, the same brain state necessitates the same pain state. That is, A-properties supervene on B-properties if being B-indiscernible implies
being A-indiscernible. The reverse does not hold: the same pain state could be "multiply realizable
" by different brain states. That is, if A-properties supervene on B-properties, being A-indiscernible does not imply being B-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 can be 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. 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 phenomena" (like those of economics, psychology, or aesthetics) depend, ultimately, on physical substance, without assuming that one can study those high-level phenomena using means appropriate to physics.
dating back to 1644.
Its systematic use in philosophy is considered to have begun in early 20th-century meta-ethics
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". The usage also carried over into the work R. M. Hare
. For discussion of the emergentist roots of supervenience see Stanford Encyclopedia of Philosophy: Supervenience.
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."
In subsequent years Terry Horgan, David Lewis
, and especially Jaegwon Kim
formalized the concept and began applying it to many 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
.
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 set of properties. 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, fact
s, or entities instead, for example.
called the "unlovely proliferation" which occurred beginning in the 1980s, inspired largely by Jaegwon Kim
's work. These varieties are based both on (1) and (2) above, but because (1) is more common we shall focus on varieties of supervenience based on it.
We can begin by distinguishing between local and global supervenience:
For example, if mental states locally supervene on brain states, then being in the same brain state entails being in the same mental state.
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:
The difference is essentially whether correlations between base and supervenient properties hold within actual 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. I have my father's 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.
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. The claim that moral properties can supervene upon non-moral properties is, however, disputed by proponents of a more restricted use of the concept.
, 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:
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 as 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.
ing. 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.
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.
, 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."
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 be consistent with our understanding of physicalism.
, 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 paradox
ical, 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".
Philosophy
Philosophy is the study of general and fundamental problems, such as those connected with existence, knowledge, values, reason, mind, and language. Philosophy is distinguished from other ways of addressing such problems by its critical, generally systematic approach and its reliance on rational...
, supervenience is a kind of dependency relationship. For example, mental states might depend on physical brain states. This dependency is typically held to obtain between sets of properties
Property (philosophy)
In modern philosophy, logic, and mathematics a property is an attribute of an object; a red object is said to have the property of redness. The property may be considered a form of object in its own right, able to possess other properties. A property however differs from individual objects in that...
. A classic example (which is not supported by scientific evidence) is that mental states of pain
Pain
Pain is an unpleasant sensation often caused by intense or damaging stimuli such as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone."...
supervene on 'C-fibers firing'
Group C nerve fiber
-Location:C fibers are found in the peripheral nerves of the somatic sensory system. They are afferent fibers, conveying input signals from the periphery to the central nervous system.-Structure:...
. According to one standard definition, a set of properties A (pain) supervenes on a set of properties B (brain), 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"). In our example, the same brain state necessitates the same pain state. That is, A-properties supervene on B-properties if being B-indiscernible implies
Entailment
In logic, entailment is a relation between a set of sentences and a sentence. Let Γ be a set of one or more sentences; let S1 be the conjunction of the elements of Γ, and let S2 be a sentence: then, Γ entails S2 if and only if S1 and not-S2 are logically inconsistent...
being A-indiscernible. The reverse does not hold: the same pain state could be "multiply realizable
Multiple realizability
Multiple realizability, in philosophy of mind, is the thesis that the same mental property, state, or event can be implemented by different physical properties, states or events...
" by different brain states. That is, if A-properties supervene on B-properties, being A-indiscernible does not imply being B-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 can be multiply realized
Multiple realizability
Multiple realizability, in philosophy of mind, is the thesis that the same mental property, state, or event can be implemented by different physical properties, states or events...
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
Reductionism
Reductionism can mean either an approach to understanding the nature of complex things by reducing them to the interactions of their parts, or to simpler or more fundamental things or a philosophical position that a complex system is nothing but the sum of its parts, and that an account of it can...
relationship. For example, many hold that economic properties supervene on physical properties, in that if two worlds
Possible world
In philosophy and logic, the concept of a possible world is used to express modal claims. The concept of possible worlds is common in contemporary philosophical discourse and has also been disputed.- Possibility, necessity, and contingency :...
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 phenomena" (like those of economics, psychology, or aesthetics) depend, ultimately, on physical substance, without assuming that one can study those high-level phenomena using means appropriate to physics.
History
Supervenience, which means literally "coming or occurring as something novel, additional, or unexpected", from "super," meaning on, above or, additional, and "venire," meaning to come, shows occurrences in the Oxford English DictionaryOxford English Dictionary
The Oxford English Dictionary , published by the Oxford University Press, is the self-styled premier dictionary of the English language. Two fully bound print editions of the OED have been published under its current name, in 1928 and 1989. The first edition was published in twelve volumes , and...
dating back to 1644.
Its systematic use in philosophy is considered to have begun in early 20th-century meta-ethics
Meta-ethics
In philosophy, meta-ethics is the branch of ethics that seeks to understand the nature of ethical properties, statements, attitudes, and judgments. Meta-ethics is one of the three branches of ethics generally recognized by philosophers, the others being normative ethics and applied ethics. Ethical...
and emergentism
Emergentism
In philosophy, emergentism is the belief in emergence, particularly as it involves consciousness and the philosophy of mind, and as it contrasts with reductionism. A property of a system is said to be emergent if it is in some sense more than the "sum" of the properties of the system's parts...
. 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". The usage also carried over into the work R. M. Hare
R. M. Hare
Richard Mervyn Hare was an English moral philosopher who held the post of White's Professor of Moral Philosophy at the University of Oxford from 1966 until 1983. He subsequently taught for a number of years at the University of Florida...
. For discussion of the emergentist roots of supervenience see Stanford Encyclopedia of Philosophy: Supervenience.
In the 1970s Donald Davidson
Donald Davidson (philosopher)
Donald Herbert Davidson was an American philosopher born in Springfield, Massachusetts, who served as Slusser Professor of Philosophy at the University of California, Berkeley from 1981 to 2003 after having also held teaching appointments at Stanford University, Rockefeller University, Princeton...
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."
In subsequent years Terry Horgan, David Lewis
David Kellogg Lewis
David Kellogg Lewis was an American philosopher. Lewis taught briefly at UCLA and then at Princeton from 1970 until his death. He is also closely associated with Australia, whose philosophical community he visited almost annually for more than thirty years...
, and especially Jaegwon Kim
Jaegwon Kim
Jaegwon Kim is a Korean American philosopher currently working at Brown University. He is best known for his work on mental causation and the mind-body problem. Key themes in his work include: a rejection of Cartesian metaphysics, the limitations of strict psychophysical identity, supervenience,...
formalized the concept and began applying it to many 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
Physicalism
Physicalism is a philosophical position holding that everything which exists is no more extensive than its physical properties; that is, that there are no kinds of things other than physical things...
), and whether it avoids or entails reductionism
Reductionism
Reductionism can mean either an approach to understanding the nature of complex things by reducing them to the interactions of their parts, or to simpler or more fundamental things or a philosophical position that a complex system is nothing but the sum of its parts, and that an account of it can...
.
Definitions
In the contemporary literature, there are two primary (and non-equivalent) formulations of supervenience (for both definitions let A and B be sets of properties).- 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
Domain of discourse
In the formal sciences, the domain of discourse, also called the universe of discourse , is the set of entities over which certain variables of interest in some formal treatment may range...
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 set of properties. 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 modalModal logic
Modal logic is a type of formal logic that extends classical propositional and predicate logic to include operators expressing modality. Modals — words that express modalities — qualify a statement. For example, the statement "John is happy" might be qualified by saying that John is...
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
Domain of discourse
In the formal sciences, the domain of discourse, also called the universe of discourse , is the set of entities over which certain variables of interest in some formal treatment may range...
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, fact
Fact
A fact is something that has really occurred or is actually the case. The usual test for a statement of fact is verifiability, that is whether it can be shown to correspond to experience. Standard reference works are often used to check facts...
s, or entities instead, for example.
Varieties of supervenience
There are many varieties of supervenience proposed in the philosophical literature, thanks in part to what David LewisDavid Kellogg Lewis
David Kellogg Lewis was an American philosopher. Lewis taught briefly at UCLA and then at Princeton from 1970 until his death. He is also closely associated with Australia, whose philosophical community he visited almost annually for more than thirty years...
called the "unlovely proliferation" which occurred beginning in the 1980s, inspired largely by Jaegwon Kim
Jaegwon Kim
Jaegwon Kim is a Korean American philosopher currently working at Brown University. He is best known for his work on mental causation and the mind-body problem. Key themes in his work include: a rejection of Cartesian metaphysics, the limitations of strict psychophysical identity, supervenience,...
's work. These varieties are based both on (1) and (2) above, but because (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 actual 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. I have my father's 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.
Value properties
The valueValue theory
Value theory encompasses a range of approaches to understanding how, why and to what degree people should value things; whether the thing is a person, idea, object, or anything else. This investigation began in ancient philosophy, where it is called axiology or ethics. Early philosophical...
of a physical object to an agent is sometimes held to be supervenient upon the physical properties of the object. In aesthetics
Aesthetics
Aesthetics is a branch of philosophy dealing with the nature of beauty, art, and taste, and with the creation and appreciation of beauty. It is more scientifically defined as the study of sensory or sensori-emotional values, sometimes called judgments of sentiment and taste...
, the beauty
Beauty
Beauty is a characteristic of a person, animal, place, object, or idea that provides a perceptual experience of pleasure, meaning, or satisfaction. Beauty is studied as part of aesthetics, sociology, social psychology, and culture...
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
Pointillism
Pointillism is a technique of painting in which small, distinct dots of pure color are applied in patterns to form an image. Georges Seurat developed the technique in 1886, branching from Impressionism. The term Pointillism was first coined by art critics in the late 1880s to ridicule the works...
), the figures and forms of the painted image, or the painted canvas as a whole. In ethics
Ethics
Ethics, also known as moral philosophy, is a branch of philosophy that addresses questions about morality—that is, concepts such as good and evil, right and wrong, virtue and vice, justice and crime, etc.Major branches of ethics include:...
, the goodness of an act of charity
Charity (virtue)
In Christian theology charity, or love , means an unlimited loving-kindness toward all others.The term should not be confused with the more restricted modern use of the word charity to mean benevolent giving.- Caritas: altruistic love :...
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
State of affairs
The state of affairs is that combination of circumstances applying within a society or group at a particular time. The current state of affairs may be considered acceptable by many observers, but not necessarily by all. The state of affairs may present a challenge, or be complicated, or contain a...
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. The claim that moral properties can supervene upon non-moral properties is, however, disputed by proponents of a more restricted use of the concept.
Mental properties
In philosophy of mindPhilosophy of mind
Philosophy of mind is a branch of philosophy that studies the nature of the mind, mental events, mental functions, mental properties, consciousness and their relationship to the physical body, particularly the brain. The mind-body problem, i.e...
, 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
Donald Davidson (philosopher)
Donald Herbert Davidson was an American philosopher born in Springfield, Massachusetts, who served as Slusser Professor of Philosophy at the University of California, Berkeley from 1981 to 2003 after having also held teaching appointments at Stanford University, Rockefeller University, Princeton...
, 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
John Haugeland
John Haugeland was a professor of philosophy at the University of Chicago from 1999 until his death. He was chair of the philosophy department from 2004-2007. He spent at most of his career teaching at the University of Pittsburgh...
, 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
Semantic externalism
In the philosophy of language, semantic externalism is the view that the meaning of a term is determined, in whole or in part, by factors external to the speaker. According to an externalist position, one can claim without contradiction that two speakers could be in exactly the same brain state at...
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 as a series of durationless moments that lie between the physical past and the physical future is known as presentism
Presentism (philosophy of time)
Saint Augustine proposed that the present is a knife edge between the past and the future and could not contain any extended period of time. This seems evident because, if the present is extended, it must have separate parts - but these must be simultaneous if they are truly part of the present...
, and is a form of belief in Galilean relativity.
Computational properties
There are several examples of supervenience to be found in computer networkComputer network
A computer network, often simply referred to as a network, is a collection of hardware components and computers interconnected by communication channels that allow sharing of resources and information....
ing. For example, in a dial-up internet connection, the audio signal on a phone line transports IP packets
Internet Protocol
The Internet Protocol is the principal communications protocol used for relaying datagrams across an internetwork using the Internet Protocol Suite...
between the user's computer and the Internet service provider
Internet service provider
An Internet service provider is a company that provides access to the Internet. Access ISPs directly connect customers to the Internet using copper wires, wireless or fiber-optic connections. Hosting ISPs lease server space for smaller businesses and host other people servers...
'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
OSI model
The Open Systems Interconnection model is a product of the Open Systems Interconnection effort at the International Organization for Standardization. It is a prescription of characterizing and standardizing the functions of a communications system in terms of abstraction layers. Similar...
of computer networking supervenes on the layers below it.
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
Glyph
A glyph is an element of writing: an individual mark on a written medium that contributes to the meaning of what is written. A glyph is made up of one or more graphemes....
, which in turn supervenes on the ink deposition on the paper.
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.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 JacksonFrank Cameron Jackson
Frank Cameron Jackson is an Australian philosopher, currently Distinguished Professor and former Director of the Research School of Social Sciences at Australian National University. In 2007-2008, he also became a regular visiting professor of philosophy at Princeton University...
, 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."
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 KimJaegwon Kim
Jaegwon Kim is a Korean American philosopher currently working at Brown University. He is best known for his work on mental causation and the mind-body problem. Key themes in his work include: a rejection of Cartesian metaphysics, the limitations of strict psychophysical identity, supervenience,...
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 be consistent with our understanding of physicalism.
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.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 entityNon-physical entity
A non-physical entity is an entity that lacks a physical or material body or material or physical characteristics. Non-physical entities may be considered hypothetical, e.g...
, 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 paradox
Paradox
Similar to Circular reasoning, A paradox is a seemingly true statement or group of statements that lead to a contradiction or a situation which seems to defy logic or intuition...
ical, 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
Hume's fork
In philosophy, Hume's fork may be used to refer to one of several distinctions and dilemmas drawn by David Hume .They are:...
which states, "there are no necessary connections between distinct existences".