- Twin Earth thought experiment
The Twin Earth thought experiment was presented by philosopher
Hilary Putnamin his 1973 paper "Meaning and Reference" and subsequent 1975 paper "The Meaning of 'Meaning'", as an early argument for what has subsequently come to be known as semantic externalism. Since that time, philosophers have proposed a number of variations on this particular thought experiment, which can be collectively referred to as Twin Earth thought experiments. Edmund Husserldeveloped a similar thought experiment nearly 70 years earlier.
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 respects, which we refer to as ‘Twin Earth’. (We should also suppose that the relevant surroundings of Twin Earth are identical to those of 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, say Oscar, 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, or Toscar, and twin-earth water as twater.) "Ex hypothesi", their brains are molecule-for-molecule identical. Yet, at least according to Putnam, when Oscar says water, the term refers to H2O, whereas when Toscar 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 Toscar 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." (Putnam 1975/1985, p.227)
In his original article, Putnam had claimed that the reference of the twins' 'water' varied even though their psychological states were the same.
Tyler Burgesubsequently argued in "Other Bodies" (1982) that the twins' mental states are different: Oscar has the concept "H2O", while Toscar 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 Toscar 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 designatorreferring 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.
Some philosophers believe that all such science-fiction thought experiments should be viewed with suspicion. 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 become unreliable, and significant philosophical conclusions cannot be drawn from them.
Daniel Dennett, for example, calls Twin Earth and other experiments like it " intuition pumps", which play on a strong but ultimately illusory intuition.
Putnam, who is well known for changing his philosophical positions on a variety of issues, criticizes the experiment later in life because it is anti-functionalist.Fact|date=July 2007
An objection to the class of Twin-Earth style arguments for externalism can be raised in the form an argument that demonstrates that externalism (semantic or content) is incompatible with privileged self-knowledge. Here, privileged self-knowledge is simply 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 disprove externalism alone, it is impressive because of the intuitive plausibility of privileged self-knowledge. Indeed, if one accepts this type of argument one is left with the option of choosing to accept either the truth of externalism or the truth of privileged self-knowledge (but not both).Fact|date=June 2008
Internalism and Externalism
* [http://host.uniroma3.it/progetti/kant/field/tea.htm Field Guide to the Philosophy of Mind article]
*Putnam, H. (1975/1985) [http://internalism.googlegroups.com/web/Putnam%20-%20The%20meaning%20of%20%27meaning%27.pdf?gda=twdJY1oAAABFSTngQf24Sy1RD7yNn1iVgy3Odg0ZctAT1N_Bh2qhdGG1qiJ7UbTIup-M2XPURDQe1sJTwbuelxnpaL6JzH4yeFMfiRQRvg6UTOJgQe0faGtRc9Sp7hcxNJ_gjwZr8bQ "The meaning of 'meaning'"] . "In Philosophical Papers, Vol. 2: Mind, Language and Reality". Cambridge University Press.
*Putnam, H. (1973). "Meaning and Reference," Journal of Philosophy 70, 699-711.
Dagfinn Føllesdal. (2001) Bolzano, Frege, and Husserl on Reference and Object. In "Future Pasts: The Analytic Tradition in Twentieth Century Philosophy". ed. Floyd, J., Shieh, Sanford. pp. 67-81(15). [http://www.oxfordscholarship.com/oso/public/content/philosophy/019513916X/acprof-019513916X-chapter-4.html]
*Pessin, Andrew and Sanford Goldberg, eds. (1996) "The Twin Earth Chronicles: Twenty Years of Reflection on Hilary Putnam's "The Meaning of Meaning"." M. E. Sharpe,
Wikimedia Foundation. 2010.
Look at other dictionaries:
Thought experiment — A thought experiment (from the German Gedankenexperiment ) is a proposal for an experiment that would test a hypothesis or theory but cannot actually be performed due to practical limitations; instead its purpose is to explore the potential… … Wikipedia
Twin paradox — In physics, the twin paradox is a thought experiment in special relativity, in which a twin makes a journey into space in a high speed rocket and returns home to find he has aged less than his identical twin who stayed on Earth. This result… … Wikipedia
Earth Sciences — ▪ 2009 Introduction Geology and Geochemistry The theme of the 33rd International Geological Congress, which was held in Norway in August 2008, was “Earth System Science: Foundation for Sustainable Development.” It was attended by nearly… … Universalium
Anarchist schools of thought — Part of the Politics series on Anarchism … Wikipedia
Hilary Putnam — Infobox Philosopher region = Western Philosophy era = 20th century philosophy color = #B0C4DE name = Hilary Whitehall Putnam birth = July 31, 1926 flagicon|USA|size=20px Chicago, Illinois school tradition = Analytic main interests = Philosophy of … Wikipedia
Functionalism (philosophy of mind) — Functionalism is a theory of the mind in contemporary philosophy, developed largely as an alternative to both the identity theory of mind and behaviourism. Its core idea is that mental states (beliefs, desires, being in pain, etc.) are… … Wikipedia
Tyler Burge — (born 1946, Ph.D., Princeton University, 1971) is a Professor of Philosophy at UCLA. He has made contributions to several areas of philosophy, including the philosophy of mind, epistemology, and the history of philosophy. In the history of… … Wikipedia
Science of morality — The Good Samaritan by François Léon Sicard. The sculpture is based on a story, and one that would be promoted by science of morality. Nature, habits, culture and norms are all pivotal in this empirical pursuit of harmony among living beings.… … Wikipedia
List of philosophy topics (R-Z) — RRaRabad Rabbinic law Rabbinic theology Francois Rabelais François Rabelais race racetrack paradox racism Gustav Radbruch Janet Radcliffe Richards Sarvepalli Radhakrishnan radical Aristotelianism radical behaviourism radical feminism radical… … Wikipedia
Internalism and externalism — See also Externalism. 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… … Wikipedia