Twin Earth thought experiment

Last updated
The Twin Earth thought experiment posits a second Earth which is identical in all ways except one BlueMarble-2001-2002.jpg
The Twin Earth thought experiment posits a second Earth which is identical in all ways except one

Twin Earth is a thought experiment proposed by philosopher Hilary Putnam in his papers "Meaning and Reference" (1973) and "The Meaning of 'Meaning'" (1975). It is meant to serve as an illustration of his argument for semantic externalism, or the view that the meanings of words are not purely psychological. The Twin Earth thought experiment was one of three examples that Putnam offered in support of semantic externalism, the other two being what he called the Aluminum-Molybdenum case and the Beech-Elm case. Since the publication of these cases, numerous variations on the thought experiment have been proposed by philosophers.

Contents

The thought experiment

Putnam's original formulation of the experiment was this:

We begin by supposing that elsewhere in the universe there is a planet exactly like Earth in virtually all aspects, which we refer to as "Twin Earth". (We should also suppose that the relevant surroundings are exactly the same as for Earth; it revolves around a star that appears to be exactly like our sun, and so on). On Twin Earth, there is a Twin equivalent of every person and thing here on Earth. The one difference between the two planets is that there is no water on Twin Earth. In its place there is a liquid that is superficially identical, but is chemically different, being composed not of H2O, but rather of some more complicated formula which we abbreviate as "XYZ". The Twin Earthlings who refer to their language as "English" call XYZ "water". Finally, we set the date of our thought experiment to be several centuries ago, when the residents of Earth and Twin Earth would have no means of knowing that the liquids they called "water" were H2O and XYZ respectively. The experience of people on Earth with water and that of those on Twin Earth with XYZ would be identical.


Now the question arises: when an Earthling (or Oscar for simplicity's sake) and his twin on Twin Earth say 'water', do they mean the same thing? (The twin is also called 'Oscar' on his own planet, of course. Indeed, the inhabitants of that planet call their own planet 'Earth'. For convenience, we refer to this putative planet as 'Twin Earth', and extend this naming convention to the objects and people that inhabit it, in this case referring to Oscar's twin as Twin Oscar.) Ex hypothesi, they are in identical psychological states, with the same thoughts, feelings, etc. Yet, at least according to Putnam, when Oscar says 'water', the term refers to H2O, whereas when Twin Oscar says 'water' it refers to XYZ. The result of this is that the contents of a person's brain are not sufficient to determine the reference of terms they use, as one must also examine the causal history that led to this individual acquiring the term. (Oscar, for instance, learned the word 'water' in a world filled with H2O, whereas Twin Oscar learned 'water' in a world filled with XYZ.)

This is the essential thesis of semantic externalism. Putnam famously summarized this conclusion with the statement that "'meanings' just ain't in the head." [1]

Criticism

In his original article, Putnam had claimed that the reference of the twins' "water" varied even though their psychological states were the same. Tyler Burge subsequently argued in "Other Bodies" (1982) that the twins' mental states are different: Oscar has the concept H2O, while Twin Oscar has the concept XYZ. Putnam has since expressed agreement with Burge's interpretation of the thought experiment. (See Putnam's introduction in Pessin and Goldberg 1996, xxi.)

A number of philosophers have argued that "water" for both Oscar and Twin Oscar refers to anything that is sufficiently water-like (i.e. the term's extension includes both H2O and XYZ). They reject, therefore, the contention that "water" is a rigid designator referring to H2O. John Searle, for example, argues (Intentionality: An Essay in the Philosophy of Mind) that, once we discover that our water is H2O, we have the choice of either redefining it as H2O (a classical reduction redefinition) or continuing to allow the term water to refer to anything with the basic properties of water (transparency, wetness, etc.). Searle suggests that in the Twin-Earth example, the second seems more plausible, since if Twin Earth doesn't have water, then all its water-based products will also be different. Twin ice cream, for example, will be constitutionally different, yet we will still be tempted to call it ice cream. Searle, along with others, considers this sufficient argument to "solve" the thought experiment altogether; others, such as Donald Davidson, feel that variations on the experiment can be used to draw some of the same conclusions.[ citation needed ]

Paul Boghossian raised an objection to the class of Twin-Earth-style arguments for externalism in the form of an argument that aims to show that externalism is incompatible with privileged self-knowledge. Here, privileged self-knowledge is taken to be the idea that one can know the content of one's thoughts without having to investigate the external world (for empirical evidence). Although this type of argument does not directly disprove externalism, it is pressing because of the intuitive plausibility of privileged self-knowledge's existence. [2]

Some philosophers believe that such science-fiction thought experiments (like the Twin-Earth) should be examined carefully. They argue that when a thought experiment describes a state of affairs that is radically different from the actual one (or what we think it to be), our intuitions can become unreliable, and hence the philosophical conclusions drawn from them may also be unreliable. Daniel Dennett calls Twin Earth and other experiments like it "intuition pumps", as they are designed in such a way to allow the thinker to use their intuition to guide them through the problem. Some philosophers take the Twin-Earth thought experiment/intuition pump to engage faulty intuitions, and hence lead to faulty conclusions. Phil Hutchinson, [3] for example, notes that a) if one looks at Putnam's own later criticisms of others (for example his criticisms of Jaegwon Kim in his book The Threefold Cord) one finds that implicitly he criticises his own earlier self; and b) that the persuasive power of the Twin Earth thought experiment/intuition pump relies on our turning a blind eye to aspects of the experiment in order that it establish that which Putnam claims it to. In short, the thought experiment is set up in such a way that one's intuitions will be pumped in the desired direction.

John McDowell, in his paper "Putnam on Mind and Meaning", [4] criticised Putnam for still having in play a latent commitment to a picture of the mind as modelled on the brain and located in the head. Putnam has since conceded the point and subscribes to McDowell's neo-Wittgensteinian therapeutic invocation of the mind as a structured system of object involving abilities (what Putnam has since defended as a neo-Aristotelian picture of mind [5] ). Phil Hutchinson has since argued that this concession to McDowell means that the distinction which Putnam wishes to operationalize, between intension and extension, is now problematized. [6]

John Dupré, in a number of papers and mainly in his paper "Natural Kinds and Biological Taxa", [7] has demonstrated that the theory of natural kinds, which many have taken to be established and/or supported by Putnam's Twin Earth thought experiment does not find support in the practice of scientific classification. Avrum Stroll has produced probably the most comprehensive critique of the program of natural kind semantics (both Putnam's and Kripke's) in his book Sketches of Landscapes. [8] Putnam, who is well known for changing his philosophical positions on a variety of issues, criticized the experiment later in life because it is anti-functionalist.[ citation needed ]

See also

Footnotes

  1. ↑ Putnam 1975/1985, p. 227
  2. ↑ Boghossian (1998): "What the externalist can know a priori".
  3. ↑ Hutchinson (2008): 'Shame and Philosophy (chapter 1, section 2).
  4. ↑ see John McDowell (1998): "Putnam on Mind and Meaning". In: id., Mind, Meaning and Reality.
  5. ↑ See his papers "Changing Aristotle's Mind" and "Aristotle after Wittgenstein", both reprinted in Putnam (1994): Words and Life.
  6. ↑ Hutchinson (2008): Shame and Philosophy (chapter 1).
  7. ↑ Reprinted in John Dupre (2002): Humans and Other Animals.
  8. ↑ Avrum Stroll (1998): Sketches of Landscapes.

Related Research Articles

Internalism and externalism are two opposing ways of explaining various subjects in several areas of philosophy. These include human motivation, knowledge, justification, meaning, and truth. The distinction arises in many areas of debate with similar but distinct meanings.

In its most common sense, philosophical methodology is the field of inquiry studying the methods used to do philosophy. But the term can also refer to the methods themselves. It may be understood in a wide sense as the general study of principles used for theory selection, or in a more narrow sense as the study of ways of conducting one's research and theorizing with the goal of acquiring philosophical knowledge. Philosophical methodology investigates both descriptive issues, such as which methods actually have been used by philosophers, and normative issues, such as which methods should be used or how to do good philosophy.

Hilary Putnam American mathematician and philosopher (1926–2016)

Hilary Whitehall Putnam was an American philosopher, mathematician, and computer scientist, and a major figure in analytic philosophy in the second half of the 20th century. He made significant contributions to philosophy of mind, philosophy of language, philosophy of mathematics, and philosophy of science. Outside philosophy, Putnam contributed to mathematics and computer science. Together with Martin Davis he developed the Davis–Putnam algorithm for the Boolean satisfiability problem and he helped demonstrate the unsolvability of Hilbert's tenth problem.

In philosophy of mind, functionalism is the thesis that mental states are constituted solely by their functional role, which means, their causal relations with other mental states, sensory inputs and behavioral outputs. Functionalism developed largely as an alternative to the identity theory of mind and behaviorism.

John McDowell South African philosopher and academic

John Henry McDowell is a South African philosopher, formerly a Fellow of University College, Oxford and now University Professor at the University of Pittsburgh. Although he has written on metaphysics, epistemology, ancient philosophy, and meta-ethics, McDowell's most influential work has been in the philosophy of mind and philosophy of language. McDowell was one of three recipients of the 2010 Andrew W. Mellon Foundation's Distinguished Achievement Award, and is a Fellow of both the American Academy of Arts & Sciences and the British Academy.

Sense and reference Distinction in the philosophy of language

In the philosophy of language, the distinction between sense and reference was an innovation of the German philosopher and mathematician Gottlob Frege in 1892, reflecting the two ways he believed a singular term may have meaning.

Brain in a vat Philosophical thought experiment

In philosophy, the brain in a vat (BIV) is a scenario used in a variety of thought experiments intended to draw out certain features of human conceptions of knowledge, reality, truth, mind, consciousness, and meaning. It is a modern incarnation of René Descartes's evil demon thought experiment originated by Gilbert Harman. Common to many science fiction stories, it outlines a scenario in which a mad scientist, machine, or other entity might remove a person's brain from the body, suspend it in a vat of life-sustaining liquid, and connect its neurons by wires to a supercomputer which would provide it with electrical impulses identical to those the brain normally receives. According to such stories, the computer would then be simulating reality and the "disembodied" brain would continue to have perfectly normal conscious experiences, such as those of a person with an embodied brain, without these being related to objects or events in the real world.

Eliminative materialism Philosophical view that states of mind, as commonly understood, do not exist

Eliminative materialism is a materialist position in the philosophy of mind. It is the idea that the majority of the mental states in modern psychology do not exist. Some supporters of eliminativism argue that no coherent neural basis will be found for many everyday psychological concepts such as belief or desire, since they are poorly defined. Rather, they argue that psychological concepts of behaviour and experience should be judged by how well they reduce to the biological level. Other versions entail the non-existence of conscious mental states such as pain and visual perceptions.

A causal theory of reference or historical chain theory of reference is a theory of how terms acquire specific referents based on evidence. Such theories have been used to describe many referring terms, particularly logical terms, proper names, and natural kind terms. In the case of names, for example, a causal theory of reference typically involves the following claims:

"Natural kind" is a label to which scholars have assigned incompatible meanings. Some treat it as a classification identifying some structure of truth and reality that exists whether or not humans recognize it. Others treat it as a human classification of knowings that work instrumentally.

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 the time of an utterance, and yet mean different things by that utterance, that is, the term picks out a different extension.

An intuition pump is a thought experiment structured to allow the thinker to use their intuition to develop an answer to a problem.

Semantic holism is a theory in the philosophy of language to the effect that a certain part of language, be it a term or a complete sentence, can only be understood through its relations to a larger segment of language. There is substantial controversy, however, as to exactly what the larger segment of language in question consists of. In recent years, the debate surrounding semantic holism, which is one among the many forms of holism that are debated and discussed in contemporary philosophy, has tended to centre on the view that the "whole" in question consists of an entire language.

In epistemology and the philosophy of mind, methodological solipsism has at least two distinct definitions:

  1. Methodological solipsism is the epistemological thesis that the individual self and its states are the sole possible or proper starting point for philosophical construction. A skeptical turn along these lines is Cartesian skepticism.
  2. Methodological solipsism is the thesis that the mental properties or mental states of an organism can be individuated exclusively on the basis of that state or property's relations with other internal states of the organism itself, without any reference to the society or the physical world in which the organism is embedded.

Twin Earth may refer to:

The analytic–synthetic distinction is a semantic distinction, used primarily in philosophy to distinguish between propositions that are of two types: analytic propositions and synthetic propositions. Analytic propositions are true or not true solely by virtue of their meaning, whereas synthetic propositions' truth, if any, derives from how their meaning relates to the world.

A priori and a posteriori are Latin phrases used in philosophy to distinguish types of knowledge, justification, or argument by their reliance on empirical evidence or experience. A priori knowledge is independent from current experience. Examples include mathematics, tautologies, and deduction from pure reason. A posteriori knowledge depends on empirical evidence. Examples include most fields of science and aspects of personal knowledge.

Epistemology or theory of knowledge is the branch of philosophy concerned with the nature and scope (limitations) of knowledge. It addresses the questions "What is knowledge?", "How is knowledge acquired?", "What do people know?", "How do we know what we know?", and "Why do we know what we know?". Much of the debate in this field has focused on analyzing the nature of knowledge and how it relates to similar notions such as truth, belief, and justification. It also deals with the means of production of knowledge, as well as skepticism about different knowledge claims.

Externalism is a group of positions in the philosophy of mind which argues that the conscious mind is not only the result of what is going on inside the nervous system, but also what occurs or exists outside the subject. It is contrasted with internalism which holds that the mind emerges from neural activity alone. Externalism is a belief that the mind is not just the brain or functions of the brain.

This is an index of articles in philosophy of language

References

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.