প্রতিধ্বতি the Echo ISSN: 2278-5264 Volume-I Issue –I, July 2012 115 প্রতিধ্বতি the Echo A journal of Humanities & Social Science Published by: Dept. of Bengali Karimganj College, Karimganj, Assam, India Website: www.thecho.in The Problem of Identity in the Identity Theory of Mind Shanjendu Nath Associate Professor, Department of Philosophy, Rabindrasadan Girls‟ College, Karimganj, Assam Email: nathshanjendu@gmail.com Abstract The identity theory of mind is advocated and developed by different philosophers beginning with Place, Feigl and Smart. The main thesis of this theory is – states and processes of the mind are identical to states and processes of the brain. Although this theory is better than dualism and Behaviourism, still it has its own problems. This theory leaves many things unexplained with regard to the relation between mind and body, which have been questioned by different thinkers in different periods. Hence, in this article I am going to find out only the problem of identity in the „Identity theory of mind‟. There is a serious objection against the mind-brain identity theory that has not been satisfactory resolved. This problem concerns various nonintentional properties of mental states on the one hand and physical states on the other. For example, after images may be green or purple in colour, but nobody could reasonably claim that states of the brain are green or purple. Moreover, it may be the case that with a fair degree of accuracy brain states are spatially located where mental states are traditionally assumed as nonspatial. The identity theory thus appears imply violation of Leibnitz‟s Law, according to which two identical things must have the common properties and thereby their differences are indiscernible. Another problem of the theory is that it fails to give a প্রতিধ্বতি the Echo ISSN: 2278-5264 Volume-I Issue –I, July 2012 116 satisfactory answer to the question of the relation and difference between mental and physical. Hillary Putnam challenges the identity theory from consideration of multiple realizibility. According to him, „pain‟ is experienced not only by humans but also by many different species of animal. However, it seems unlikely that all these diverse organisms with the same pain experience are in the same identical brain state. Moreover, if the latter is the case, then pain cannot be identical to a specific brain state. J. R. Searle puts forward certain problems for the identity theory. He states that identity theory violates the principle of logic called "Liebnitz Law". According to this law, any two things are called identical if and only if all the properties, which they bear, are found common to both of them. This means that the properties that we find in one thing are also the properties, which we find in another thing. If this law is violated, that is, if it is possible to show that the properties of mental state cannot be attributed to brain and viceversa then it refutes the identity theory. There is another objection against the identity theory. If the identity of mental states and brain states are empirical one, that is if the identity is discovered empirically, for example, if it could be discovered on the analogy with water and H2O, or lightning and electrical discharge, then it seems that there would have to be two kinds of properties which will define the two sides of identity statement. Moreover, these two kinds of properties must identify one and the same thing. Thus, when it is said by the identity theorists that „lightning is identical with an electric discharge‟ they must have to identify one and the same thing in terms of the properties of lightning and the properties of electrical discharge, or when it is said that „water is identical with H2O molecules‟ has to identify one and the same thing in terms of the properties of water and the properties of H2O. Thus, when the identity theorists claim that „pain is identical with a certain types of brain state‟ they have to identify one and the same thing in terms of the properties of pain and the properties of brain-state. Nevertheless, problem arises if it is believed that in the identity statement, there are two sets of properties and these properties are independent. In that case, it appears that there are two different types of properties – mental properties and physical properties. And this belief of two sets of properties takes us back into property dualism. প্রতিধ্বতি the Echo ISSN: 2278-5264 Volume-I Issue –I, July 2012 117 Again, if it is true that all mental states are brain states, then what appears is that brain states are of two kinds – mental states and non-mental states. The mental states of brain have mental properties and those of non-mental states of brain have only physical properties. If it is so, then it sounds like property dualism. Another objection slightly more technical was labelled against the identity theory and this was the accusation of „neuronal chauvinism‟. This objection really vibrated the identity theorists and they were indeed forced to do some modification in their theory. This charge was highlighted by Searle and says- "If the claim of the identity theorists was that every pain is identical with a certain kind of neuronal stimulation, then it seems that a being that did not have neurons or that did not have the right kind of neurons could not have pains and beliefs. But why cannot animals that have brain structures different from ours have mental states? And indeed, why could not we build a machine that did not have neurons at all, but also had mental states?" Searle claims that facing this objection the identity theorists are bound to shift from what is called „type–type identity theory to „token–token identity theory‟. Thus in order to establish this claim Searle explains the distinction between type and token. Write the word "cow" three times: "cow" "cow" "cow". A question arises whether one word or three words are written. It is not debatable that here one type of word is written in three instances, or three tokens of one word is written. By types he means abstract general entities and by tokens he illustrates those which are concrete particular objects and events of those abstract generals. Thus when it is said that „a token of a type‟ it means that it is a particular concrete example of abstract general type. Let us now see how Searle proves that the identity theorists are moved from a type–type identity theory to a token-token identity theory. According to him, it is the point of the type-type identity theory that every type of mental state is identical to some type of physical state. Searle claims that by their own assertion it is a bit sloppy of the identity theorists. Because the identity in question is not between abstract universal types but between actual concrete tokens. What the identity theorists mean is that for every mental-state, type there is some brain-state type and thereby every token of the mental type is nothing but a token of the brain type. The simple version of the token identity theorists, according to Searle, isপ ্রতিধ্বতি the Echo ISSN: 2278-5264 Volume-I Issue –I, July 2012 118 "for every token of a certain type of mental state, there is some token of some type of physical state or other with which that mental state token is identical. They, in short, did not require, for example, that all token pains had to exemplify exactly the same type of brain states even though they were all tokens of the same mental type, pain. For that reason they were called „token-token‟ identity theorists as opposed to „type-type‟ identity theorists." Searle claims that tokentoken identity seems to be more plausible than type-type identity. In this connection, he cites an example that two persons may have same belief that „Denver is the capital of Colorado but it is not necessary to suppose that they have exactly the same type of neurobiological state. The neurobiological state of one‟s belief might be at a certain point of his brain and another‟s might be at another point although they have the same belief. Searle thinks that in giving examples the identity theorists are often found very weak and this is unfortunate. Although they have given different examples, the favourite one is that pains are identical with C-fibre stimulations. But in giving this example both „type-type‟ and „token-token‟ identity theorists differ in certain extent. The former believes that every pain is identical with some C-fibre stimulation whereas the latter believes that not every pain but particular pain might be identical with particular C-fibre stimulation. Regarding other pains, they think that this might be identical with some other state of a brain or machine. However, all these are designated by Searle as „bad neurophysiology‟. In explaining, the status of C-fibre Searle says that C-fibres are a type of axon, which carries certain types of pain signals to the brain. Pain mechanism is a complex one in the brain and nervous system and C-fibre is just a part of this complex mechanism. Thus, neurophysiologically it would be ridiculous to think that except Cfibre stimulation, there is nothing in the pain. Thus, there is a good deal of debate centered round the question whether or not we would get such type of identity as exemplified by the type-type identity theorists. Or is it token identity upon which we could hope for. Searle believes that in between type and token identity, it is latter one, which is more influential than the former. In spite of its acceptability, the token identity theorists have been facing another question and this is the question of commonness. What common things are there in all of these tokens, which make the same mental state type? If it is believed প্রতিধ্বতি the Echo ISSN: 2278-5264 Volume-I Issue –I, July 2012 119 by both X and Y that Denver is the capital of Colorado then apart from their brain state what exact thing is common in them but again both X and Y have different types of brain states? There are two answers that we find traditionallyone is from the dualist‟s quarter and another from type-type. However, none of these answers will do for the token physicalist. Because the whole idea of the token identity theorists is to eliminate any type of irreducible mental properties and as such they cannot accept that the common thing in between X and Y is same irreducible mental properties. Again, the token theorists cannot accept the view that the same type of brain state is common in X and Y because it is this point disagreeing upon which there is move from type identity to token identity. Thus the answer that a particular mental state type and certain brain state type are identical cannot save the identity theorists from their downfall. Soul Kripke also raised an objection against type-type identity theory from consideration of rigid reference. The identity theorists claim that the identity of mental and brain states are contingent. But Kripke argues that this identity is necessary, if true. He introduces two types of designators of entity, namely, rigid and non-rigid designators and holds that rigid designators refer to the same entity in every possible world and therefore identity of two entities referred by two rigid designators are necessary. Non-rigid or flaccid designators may refer to different entities in different possible worlds and identities of their referents thereby are contingent. The expression „Benjamin Franklin‟, which always refers the same person is a rigid designator. The expression „The inventor of daylight saving time‟ which, according to him, is a non-rigid designator, although this expression refers to Benjamin Franklin in the actual world. In a possible world, Benjamin Franklin may not be the inventor of daylight saving time. Anybody else other than Benjamin, the actual inventor, might have been the inventor of daylight saving time. On the other hand, it is not the case that someone else, other than Benjamin Franklin, might have been Benjamin Franklin. It is due to this reason Kripke says that „Benjamin Franklin‟ is a rigid designator, where as „the inventor of daylight saving time‟ is nonrigid. Thus with these two types of designators Kripke examines the mind-body identity statement. He claims that if one term is rigid and another is non-rigid in an identity statement, the statement is not necessarily true and it might turn out to be false. Thus the প্রতিধ্বতি the Echo ISSN: 2278-5264 Volume-I Issue –I, July 2012 120 statement „Benjamin Franklin is identical with the inventor of daylight saving time‟ is true no doubt but this truth is contingent one because there may be a possible world where this statement is false. Kripke says that a statement must be necessarily true if it is the case that both sides of the identity statement are rigid and the statement is true. In this connection he cites the statement „Samuel Clemens is identical with Mark Twain‟ and says that this statement is necessarily true because here both sides of the above statement mean one and the same person. It is impossible to imagine that there is a world where Samuel Clemens exists and also Mark Twain exists but they are not one and the same person but two different individuals. This is also true in the case of words that name natural kinds of things, for example, the statement „water is identical with H2O‟. Here both the expressions „water‟ and „H2O‟ are rigid and the stament is true, therefore, this identity is necessary. Kripke finds the relevancy of this kind of argument in the case of mind-body problem. He says that if it is found that both the expressions „mental state‟ and „brain state‟ refer rigidly and the identity statement containing those expression is true then the statement must be necessarily true. Thus „pain is equivalent to C-fibre stimulation‟ would have to be necessarily true if it is the case that pains were really identical with C-fibre stimulations. Here all these depend on the condition that if it were to be true at all. But Kripke claims that this statement is not necessarily true. Because it can be imagined that there exists pain without a C-fibre stimulation and also C-fibre stimulation without pain, although pains and C-fibre stimulations have strict correlations in this world. Thus Kripke logically concludes that if the statement „pain is identical with C-fibre stimulation‟ is not necessarily true on the ground mentioned above then it cannot true at all, and hence it is false. His suggestion regarding identification of pains and neurobiological events is that there is a hope for identity theory if it is really the ide Reference Feigl, H. 1958: „The "Mental" and the "Physical" ‟. In Feigl, H., Scriven, M. and Maxwell, G. (eds.) Concepts, Theories and the MindBody Problem, Minneapolis, Minnesota Studies in the Philosophy of Science, Vol. 2, reprinted with a Postscript in Feigl 1967. প্রতিধ্বতি the Echo ISSN: 2278-5264 Volume-I Issue –I, July 2012 121 Feigl, H. 1967: The „Mental‟ and the „Physical‟, The Essay and a Postscript, Minneapolis, University of Minnesota Press. Kripke, S. 1980: Naming and Necessity, Cambridge, Mass., Harvard University Press. Place, U.T. 1960: „Materialism as a Scientific Hypothesis‟, Philosophical Review, 69, 101-104. 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