There are a few problems with the Twin-Earth



In a really of import article entitled “The Meaning of Meaning, ” Hilary Putnam suggested a thought experiment about a topographic point referred to as Twin Earth. Upon using such a thought experiment and seeking the branchings of this experiment, Putnam thought to demo an deduction sing what have been called “natural kind” footings. At least one deduction of his thought experiment and go toing statements is that such footings do be, and they have of import deductions sing causality and, possibly less significantly to Putnam, kernels. His logical thinking and deductions have been adhered to by some ( e.g. , Saul Kripke ) , but countered and repudiated as finally untenable by others ( e.g. , D. H. Mellor, John Dupre and Jessica Brown ) . It is interesting to observe that the lines of statement offered by these assorted oppositions are all rather different from one another, and non ever successful. It will be further a farther captivation of the present writer that each and everyone of these critics will neglect to turn to what seems to be the greatest failings of Putnam’s statement.

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Possible Worlds and Twin Earth

At the clip when Putnam’s article appeared to the wide philosophical community ( 1975 ) , possible universes ontology was all the fury. Even to this twenty-four hours, it seems to hold subsided merely a small in the philosophical diaries and books. It is ab initio interesting to see that the full statement for Twin Earth is predicated on the reader’s silent premise along with Putnam that possible universes ontology and go toing thought experiments like the 1s he offers are either licit or even agreeable to the reader. It has been argued by an tremendous sum of twentieth-century realists ( i.e. , anti-idealists ) that such ontology is non to be recommended. [ 1 ] Furthermore, any kind of idea experiments that arise from it will be unpersuasive and, what is worse, wrongheaded because they presuppose the legitimacy of that peculiar attack to philosophy which renders many more jobs than it does solutions ; viz. , idealism. But, we shall reserve infinite subsequently to acquire more to a great extent into these types of reactions to Putnam’s statements. For now, we must show Twin Earth and larn from its protagonists and disparagers what we might reap as helpful or non.

In the subdivision of the article entitled “Are significances in the caput? ” Hilary Putnam has the reader engage in a thought experiment that has one assume that there is someplace ( wherever one illusions it might be ) another universe entirely like our ain. There is no sense ( salvage one ) in which this universe differs from our ain. Name this other universe, which is merely like a twin to ours, “Twin Earth.” There exists Earth as it is today and into the past ( e.g. , in 1750 ) and there is Twin Earth as it is today and into its yesteryear of 1750 and beyond. Not merely is Twin Earth wholly indistinguishable to our ain now, but they two universes portion the exact same history and peoples. Everything on Earth has an identical reproduction on Twin Earth, including the reader. The reader has an indistinguishable person on Twin Earth with whom there is no differentiation.

However, there is one important difference between the two universes. On Earth, the liquid we all today ( and in 1750 ) call H2O is H2O. On Twin Earth the experientially same liquid that corresponds to our H2O has the chemical composing of XYZ, implying that the two are non indistinguishable substances. They have different chemical composings even though they are experientially the same.

Now see a brace of transworld twins, Tony Blair and Twin Tony. [ 2 ] A natural catastrophe has occurred at the same time in both universes. Tony Blair and his matching Twin on Twin Earth respond by bespeaking that we need to acquire nutrient and “water” to the victims every bit rapidly as possible. But, of class, when each utters this statement, they do non hold the same significances in their heads. Twin Tony intends that we get nutrient and XYZ to his victims while Tony Blair means that we should acquire nutrient and H2Oxygen to his matching victims. Putnam provinces, “ [ Today ] likely every grownup talker even knows the necessary and sufficient status ‘water is H2O’…” ( Putnam, 228 ) . And, of class, Putnam writes this with mention to the existent Earth.

So what is the upshot of all of this for Putnam? The deduction is that Blair’s and Twin Blair’s encephalon provinces are non the lone things finding their significances. “For their encephalon provinces and bodily provinces are indistinguishable, yet their vocalization significances differ, ” ( Lycan, 67 ) . Presumably so, this illustration shows that intending ain’t simply in the caput. There is some kind of causal nexus between what is known and the apprehender, and it does non merely travel one manner ( from the apprehender to the universe ) but besides goes in the contrary order ( from the universe to the apprehender ) . Such a causal relationship is situated within an “externalist” position of intentionality, which “regards knowing provinces of head as owing their content ( what they are of or about ) to causal dealingss agents bear to the universe, ” ( Heil,Doctrine of Mind,215 ) .

Saul Kripke supports this line of logical thinking of Putnam and argues further that there is, he agrees with Putnam, some weak sense of necessity owing to our experiential statements like “cats are animals.” This sense of necessity arises from the fact of externalism. Such statements of class do non transport the force of necessity of others like “bachelors are non married.” Still, owing to this sense of externalism for which Putnam has argued there is some type of necessity retention, since there is a causal relation coming from the thing known to the apprehender. Kripke writes, “The illustration he [ Putnam ] gives is ‘cats are animals’ . Cats might turn out to be automata, or strange demons…Suppose they turn out to be a species of devils. Then on his position, and I think besides my position, the disposition is to state, non that there turned out to be no cats, but that cats have turned out non to be animate beings as we originally supposed, ” ( Kripke, 122 ) . Indeed, this would be a type of realistic position, or at the really least an externalist position.

Some Detractors

But, of class non everyone is persuaded by this thought experiment of Putnam, nor by the support of Kripke. Let us get down with he who is least sympathetic and most polemical toward Putnam: D. H. Mellor. From Mellor’s stance, he is clearly anti-essentialist: a self-proclaimed “Fregean” who is opposed to Aristotelean kernels ( Mellor, 135 ) . Small admiration so that his remarks try to come at Putnam’s concluding with such force.

Mellor’s manner of trying to sabotage the Putman illustration of the Twin Earth is to demo that

It is so rather field to my Fregean oculus that in 1950, as in 1750, ‘water’ had the same extension on Twin Earth as it had here. There was H2O on both planets likewise, and there still is. We merely discovered that non all H2O has the same microstructure ; why should it? Because its microstructure is an indispensable belongings of H2O? Well, that is what’s in inquiry ( Mellor, 127 ) .

What is seen here in this remark is that Mellor does non accept the decision arrived at by Putnam. This is non to state that he does non accept the externalist decision ( which he surely does non ) . We mean to state that he does non even accept that which Putnam assumes most everyone will accept: that H2O is, needfully, H2O. But, merelyPrima facieit seems that this manner of reasoning against Putnam is finally unsuccessful. It leads to an uneven decision that non all H2O would hold to hold the same microstructure ( Mellor, 127 ) . On this position so, non merely would H2O non hold to intendmerelyHydrogen2O, it could intend somethingwhollydifferentfrom H2O-it could intend XYZ. This is a surprising and non wholly plausible option, which would non at wholly be that easy to decide.

John Dupre clearly repudiates this line of concluding in a decidedly realist, or at least empiricist, manner. For Dupre, the possibility that there could be “water” on both planets that does non hold the same “microstructure” is wholly implausible, if non experientially impossible. Surely experience must be some kind of counsel against such highly idealistic guesss. All scientific experience suggests that such an happening as Putnam describes is non well-founded. That two substances would be the same in all respects save that facet of molecular construction is ne’er encountered in nature by the scientific community. Furthermore, “it is certainly merely the absence of experiences like the one Putnam describes that makes it sensible to attach to molecular construction at least most of the importance that Putnam ascribes to it, ” ( Dupre, 72 ) .

Clearly Putnam does impute unbelievable significance to it. Remember that for Putnamn “water is H2O” is a necessary and sufficient definition. It seems so that to construct an full statement from that which goes contrary to the whole of scientific history would be non really steady evidences at all. So Dupre here argues against both Putnam and Mellor. However, Mellor is non finished with his contentions, and for this following statement he can even delight Dupre’s scientific pragmatism. Mellor writes,

There is a perfect case in point in the find of isotopes…the two common isotopes of Cl. Note that in these existent instances the assorted isotopes occur together in natural samples ; they aren’t segregated onto separate planets. It is hence undeniable that the extension of ‘chlorine’ included both isotopes before their find, and so presumptively includes both isotopes now ( Mellor, 127 ) .

From this statement, Mellor seems to be stating that when we come to a Fuller cognition of what something is as scientific discipline advancements, but this farther cognition does non do us to reject what was “known” antecedently, as if what was thought to be the nature Cl in the yesteryear was untrue. No, it was non entirely true, though what was said to be known of it was, in some limited manner, true. This does look to be an equal statement against Putnam’s excessively scientific presupposition of specifying natural things in footings of their chemical make-up, but I will cover more with this below.

Jessica Brown has a somewhat different return on Putnam and Kripke. On the whole she is persuaded that natural sort footings exist.

Kripke and Putnam claim, and it seems independently plausible, that a community can hold natural sort footings in its linguistic communication even in progress of cognizing the right scientific history of those kinds… . [ But ] As Kripke and Putnam point out, natural sort footings apply to points in virtuousness of their ownership of certain cardinal belongingss, where it is the occupation of the scientist to state us what those cardinal belongingss are. ( Brown, 276 )

Whether it could be true that one must depend on a scientist to state us what the belongingss of things are remains to be seen, but we will cover more with this in the independent review below. However, thought Brown agrees with the decisions arrived at by Kripeke/Putnam, she attempts a figure of expostulations to Putnam’s theory which do non look, in the sentiment of this writer, to hold the force she believes they do. She grounds in one topographic point that a peculiar type of expostulation to Putnam’s theory exposes its failing. This is a higher-level natural sort job. She explains,

The higher-level natural sorts job arises from the fact that, typically, if an point instantiates one natural sort it besides instantiates others. To take a few illustrations in the instance of substance sorts, a diamond instantiates diamond and C ; a sample of H2O instantiates H2O and liquid, and a sample of sulfuric acid instantiates sulfuric acid and the more general natural sort of acid. ( 279 )

This is ab initio interesting but besides a small puzzling. It seems that Mellor has already met this type of expostulation by reasoning that we knowmore thanwhat was known antecedently when we run across scientific promotion, nonless than.Besides, what does the phrase “a sample ofH2OinstantiatesH2Oand liquid” mean? ‘Water instantiates water’ is without any important significance it would look. So, it is a small ill-defined what is precisely being argued, but if it is what was supposed supra, so Mellor and others have answered it successfully plenty.

Then there is the composing job that she presents, which states that most happenings of H2O ( which if we mean by thatmerelyHydrogen2O so we have a job ) have in them H2O, D2O, H2Oxygen2,salt, and other minerals… . So, this is opposed to what she takes Putnam to by connoting in his reductive definition of “water is H2O.” There is some force to this statement, but Brown goes on to do unusual claims though, like the followers: “However, impure samples of H2O do non instantiate H2O, ” ( 281 ) . Again, the answer to this kind of unfavorable judgment remains changeless. When one comes to cognize more about a certain object that does non needfully connote that what was known antecedently was in mistake. One has to inquire howH2Owould non instantiateH2O, as she says. It seems that she falls victim to the type of unfavorable judgment she levies against Putnam and Kripke. And finally, the large job is that her unfavorable judgments do non truly hit at the Putnam statement, unless H2O is all and merely H2O. But, she even admits that this does nonneedfullyhold to be the instance for Putnam ( Cf. Brown, 283, n.10 ) .

Some More Detraction

There are non a few more jobs with the Twin-Earth illustration, it seems. Some of these jobs seem instead big and in demand of heavy defence ( that is, they are metaphysical jobs ) , but others are possibly merely in demand of farther elucidation from Putnam-type places. If I have understood Putnam right, the head job he encounters consists in its idealistic ( “possible worlds” ) nature. Extra to this, is the implicit in presupposition towards specifying something which exists, non in an Aristotelean manner ( the “nature” of a thing-what itis) , but instead in an overly scientific manner.

That is to state, Putnam seems to take it as obvious that to inquire the inquiry “what is H2O? ” is precisely the same as inquiring the inquiry “of which chemical elements does the simple compound H2O consist? ” Now, the fact that these two inquiries would illicit really different replies would presumptively be adequate to demo that the two inquiries are non at all the same. If I ask an person “what is H2O? ” I am seeking an reply that would travel toward informing me of the assorted properties of H2O. That is, I am seeking an reply along the line of substance, which, harmonizing to metaphysics of any Aristotelean spirit, iswhata thing is. [ 3 ]

In this instance of H2O, one might specify it therefore: ‘a naturally-occurring, clear, odourless, tasteless liquid.’ The reply to the 2nd inquiry, of class, is ‘H2O.’ It seems evident that there is something unnecessarily and scientifically reductive about Putnam’s definition of H2O. It does non look at all appropriate to offer H2O as an reply to the inquiry, “what is H2O? ” For in this peculiar inquiry H2O is non an reply. In inquiring about H2O, I wish to cognize what can truly and to the full be predicated of this peculiar thing in the universe. To give the reply H2O is to merely give a really partial and discipline-restricted reply. It is restricted to the subject or scientific discipline of chemical science. Outside of this badly limited context, it has no relevancy to the inquiry “what is H2O? ” The consequence of this petty criticism from Putnam’s “scientism” is that one would today state that H2O is “a naturally-occurring, clear, odourless, tasteless liquid whose chemical make-up is H2O.” So, as cognition progresses one does non throw away what was believed about an object in world when he comes to cognize somethingmoreabout it. He simply incorporates the new penetration which is non at all opposed to everything antecedently believed.

Some Concluding Ideas

The other reserve one might hold to the Twin Earth illustration Putnam raises is its built-in possible nature, as opposed to being an statement based on the existent. Presumably it is non excessively controversial to province that an statement originating from that which is existent carries more weight than an statement based on little more than a thought-experiment, the being of which is limited to the head. That is, Twin Earth and any attending physical features is has are limited to the head, since no entreaty is made to what which is existent in depicting it. It is, rather literally, aidea-experiment, instead than an experiment holding to make with what really exists independent of ideaandthought itself. But, what would this affair to most? It is merely a cautiousness that is offered here, and the cautiousness that one should mistake in favour of pragmatism. The basic realist place has been summed up by Etienne Gilson in the undermentioned mode:

Basically, it consists in a considered pick between two possible methods, Aristotle’s and Descartes’ . Either one begins with being, in which though is included—ab esse ad nosse gentleman consequentia; or one starts from idea, in which being is included—a nosse ad esse gentleman consequentia.

It is all really good and ticket to prosecute in possible universes scenarios harmonizing to the current philosophical clime, and it would be far excessively big a undertaking to seek to turn over such dispositions. However, one should at the really least be cognizant of “realistic” options out at that place, which stand in direct resistance to such thought experimentation where one derives an full matured statement based, non on what one experiences in world ( nor even on the contemplations thereof ) , but instead on a conjecture-a Twin Earth. It does non look that one would keep with Putnam his grounds for believing in natural sort words. Whether such things are existent would be agreed-upon by many realists and detracted from by many other utmost empiricists. It was our end in this paper to reason whether Putnam has substantiated the being of such words ( otherwise, if he had non, it would be mere fortune that he stumbled upon them as really bing things, when his manner of acquiring to them was erroneous ) , and it seems that his places do non stand up to the critical examination of many foreparts.


Brown, John. “Natural Kinds and Biological Taxa, ” inPhilosophical Reviewv.90 no.1 Jan, 1981, 66-90.

Dupre, Jessica. “Natural Kind Footings and Recognitional Capacities, ” inMindv.107 no.426 April, 1998, 275-303.

Gilson, Etienne.Methodical Realism.Tr. Philip Trower. Front Royal, VA: Christendom Press, 1990.

Heil, John.Doctrine of Mind: A Contemporary Introduction.New York: Routledge, 1998.

Kripke, Saul A.Naming and Necessity.Oxford: Basil Blackwell, 1980.

Lycan, William G.Doctrine of Language: A Contemporary Introduction.New York: Routledge, 2000.

Loux, Michael J.Metaphysicss: A Contemporary Introduction.New York: Routledge, 1998.

Mellor, D. H. “Natural Kinds, ” inMatters of Metaphysicss.New York: Cambridge University Press, 123-35.

Putnam, Hilary. “The significance of ‘Meaning, ’” inMind, Language and Reality.New York: Cambridge University Press, 215-271.


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