1. Philosophy 4610 Philosophy of Mind Week 5: Functionalism

2. Theories of Mind: RECAP DUALISM (Descartes): Mind and body are distinct substances. Body is physical and exists in physical space, but the mind is non-physical and does not exist in physical space DUALISM (Descartes): Mind and body are distinct substances. Body is physical and exists in physical space, but the mind is non-physical and does not exist in physical space PHYSICALISM: Everything in the world, including “minds”, is physical. What we talk about when referring to the “mind” is just physical processes and events. PHYSICALISM: Everything in the world, including “minds”, is physical. What we talk about when referring to the “mind” is just physical processes and events.

3. Theories of Mind: RECAP PHYSICALISM breaks down into a number of distinct sub-theories: PHYSICALISM breaks down into a number of distinct sub-theories: –Logical Behaviorism: Mental states are just ways of behaving, or being disposed to behave. –Identity Theory: Mental states (states of the mind) are identical with physical states of the brain. –Functionalism: Mental states are functional states of the whole organism.

4. Functionalism The Functionalist theory of mind was first proposed by Putnam and a few others in the early 1960s The Functionalist theory of mind was first proposed by Putnam and a few others in the early 1960s Though it is usually understood as a physicalist theory, it is an alternative to both behaviorism and the identity theory. Though it is usually understood as a physicalist theory, it is an alternative to both behaviorism and the identity theory.

5. Multiple realizability: An objection to the Identity Theory According to the Identity Theory, every mental state is identical to a brain state. According to the Identity Theory, every mental state is identical to a brain state. For instance, the state of being in pain might be identical to brain state R1, a certain rate of neurons firing in the temporal lobes. For instance, the state of being in pain might be identical to brain state R1, a certain rate of neurons firing in the temporal lobes.

6. Multiple realizability: My pain and squid pain However, a squid or a Martian can also be in a state of having pain. However, a squid or a Martian can also be in a state of having pain. But the squid’s brain is essentially different from mine: although the squid has pain, it is never in state R1. But the squid’s brain is essentially different from mine: although the squid has pain, it is never in state R1. It follows that the identity theory’s identification of pain with state R1 must be incorrect It follows that the identity theory’s identification of pain with state R1 must be incorrect

7. Functionalism: Multiple Realizability “Consider what the brain-state theorist has to do to make good his claims. He has to specify a physical-chemical state such that any organism (not just a mammal) is in pain if and only if (a) it possesses a brain of a suitable physical chemical structure; and (b) its brain is in that physical- chemical state...” (p. 77) “Consider what the brain-state theorist has to do to make good his claims. He has to specify a physical-chemical state such that any organism (not just a mammal) is in pain if and only if (a) it possesses a brain of a suitable physical chemical structure; and (b) its brain is in that physical- chemical state...” (p. 77) But this is implausible. We need a more general way of identifying mental states with states of the organism (if we still want to be physicalists at all) But this is implausible. We need a more general way of identifying mental states with states of the organism (if we still want to be physicalists at all)

8. Functionalism These considerations led Putnam to suggest the functionalist theory of mind. These considerations led Putnam to suggest the functionalist theory of mind. “I shall... argue that pain is not a brain state in the sense of a physical-chemical state of the brain (or even the whole nervous system), but another kind of state entirely. I propose the hypothesis that pain, or the state of being in pain, is a functional state of the whole organism.” (p. 75) “I shall... argue that pain is not a brain state in the sense of a physical-chemical state of the brain (or even the whole nervous system), but another kind of state entirely. I propose the hypothesis that pain, or the state of being in pain, is a functional state of the whole organism.” (p. 75)

9. What is a functional state? -A functional part of an organism or system is defined in terms of what it does rather than what it is composed of or what actual shape it takes. -Example: Brakes

10. What is a functional state? Similarly, a functional state can be defined in terms of what the organism does rather than the actual composition of the internal state. Similarly, a functional state can be defined in terms of what the organism does rather than the actual composition of the internal state. Example: being thirsty. We might define being thirsty in terms of the organism’s tendency to move toward water, to drink, etc. Example: being thirsty. We might define being thirsty in terms of the organism’s tendency to move toward water, to drink, etc.

11. Functionalism vs. Identity Theory If this is right, then one and the same functional state – e.g. being thirsty – can be identical with a variety of different brain states in different organisms. One and the same function can be served by a variety of different brain states. If this is right, then one and the same functional state – e.g. being thirsty – can be identical with a variety of different brain states in different organisms. One and the same function can be served by a variety of different brain states. Thus, the functionalist avoids the problem of multiple realizability that made trouble for the identity theorist Thus, the functionalist avoids the problem of multiple realizability that made trouble for the identity theorist

12. Functionalism vs. Behaviorism For the functionalist, mental states are recognized by the behavior they cause: “…let us begin with the fact that we identify organisms as in pain, or hungry, or angry, or in heat, etc., on the basis of their behavior” (p. 77) For the functionalist, mental states are recognized by the behavior they cause: “…let us begin with the fact that we identify organisms as in pain, or hungry, or angry, or in heat, etc., on the basis of their behavior” (p. 77) But they are not identical with these behaviors (as the logical behaviorist would hold). Rather, the functional state is whatever underlying state causes the behavior, without being identical with it. But they are not identical with these behaviors (as the logical behaviorist would hold). Rather, the functional state is whatever underlying state causes the behavior, without being identical with it.

13. Functionalism: The Computer Model of Mind Another important influence on Putnam, and on functionalism in general, is the analogy between minds and computers. Another important influence on Putnam, and on functionalism in general, is the analogy between minds and computers. Like minds, computers can be defined purely functionally without reference to the actual physical parts that make them up. Like minds, computers can be defined purely functionally without reference to the actual physical parts that make them up.

14. The computer model of mind When Putnam wrote in the early 1960s, computer technology was still at an early stage. Computers took up a lot of space, and weren’t very fast. When Putnam wrote in the early 1960s, computer technology was still at an early stage. Computers took up a lot of space, and weren’t very fast. Today computers have advanced a great deal and come to be a part of almost every aspect of our daily lives. Today computers have advanced a great deal and come to be a part of almost every aspect of our daily lives.

15. Functional analysis The computer model of mind holds that minds, like computers, are simply complex information-processing systems that can be analyzed in functional terms. The computer model of mind holds that minds, like computers, are simply complex information-processing systems that can be analyzed in functional terms. To give a functional analysis, we begin by thinking about what the system or organism does as a whole. To give a functional analysis, we begin by thinking about what the system or organism does as a whole. Then we start thinking about what functionally described and related parts are needed to accomplish this. Then we start thinking about what functionally described and related parts are needed to accomplish this.

16. Functional analysis Example: human face-recognition Example: human face-recognition We can give a general functional description in terms of information flow without knowing anything about the actual physical make-up of the system that is carrying out these functions. We can give a general functional description in terms of information flow without knowing anything about the actual physical make-up of the system that is carrying out these functions. If the computer model is right, then it is the job of cognitive science to give such a description or analysis, without worrying about the specific material basis of the parts described. If the computer model is right, then it is the job of cognitive science to give such a description or analysis, without worrying about the specific material basis of the parts described.

17. The computer model: Turing Machines In the late 1940s – before there even were computers at all – Alan Turing gave a general functional model that actually works as a description of all actual computers, and more generally all information-processing systems. In the late 1940s – before there even were computers at all – Alan Turing gave a general functional model that actually works as a description of all actual computers, and more generally all information-processing systems.

18. Turing machines

19. The Turing machine is a kind of general functional architecture for any computer or any information-processing system whatsoever. The Turing machine is a kind of general functional architecture for any computer or any information-processing system whatsoever. Turing machines are also multiply realizable – we can build them out of whatever materials we like. In fact, the description of the Turing machine “program” has nothing to do with the physics or chemistry of the actual underlying states. Turing machines are also multiply realizable – we can build them out of whatever materials we like. In fact, the description of the Turing machine “program” has nothing to do with the physics or chemistry of the actual underlying states.

20. The computer model and cognitive science The idea of functional description and the computer model gave scientists access to a very general and abstract way of talking about mind in terms of what they do. The idea of functional description and the computer model gave scientists access to a very general and abstract way of talking about mind in terms of what they do. This allowed researchers in artificial intelligence, computer science, psychology, engineering, and many other fields to address a unified subject- matter: the science of information-processing (whatever the material basis or substrate). This allowed researchers in artificial intelligence, computer science, psychology, engineering, and many other fields to address a unified subject- matter: the science of information-processing (whatever the material basis or substrate). This is what came to be called “cognitive science.” It brings together research in all these different fields into a unified field of study of information- processing systems, defined in functional terms. This is what came to be called “cognitive science.” It brings together research in all these different fields into a unified field of study of information- processing systems, defined in functional terms.

21. Functionalism and the computer model: Summary Functionalists are (usually) physicalists, but instead of identifying mental states with behavior or with physical brain states, they identify them with functionally described states of the whole organism. Functionalists are (usually) physicalists, but instead of identifying mental states with behavior or with physical brain states, they identify them with functionally described states of the whole organism. This allows them to identify and describe mental states that can be shared even by organisms or systems with very different material substrates. This allows them to identify and describe mental states that can be shared even by organisms or systems with very different material substrates. Functional analysis treats the mind as an information- processing system – on the level of functional description, essentially the same as a computer. Functional analysis treats the mind as an information- processing system – on the level of functional description, essentially the same as a computer. By allowing researchers in different areas of psychology and engineering to communicate, this model of mind has proved deeply influential in the development and growth of “cognitive science” from the 1960s to today. By allowing researchers in different areas of psychology and engineering to communicate, this model of mind has proved deeply influential in the development and growth of “cognitive science” from the 1960s to today.