Section 2.2 You Are What You Eat Mind as Body 1

Empiricism Empiricism claims that the only source of knowledge about the external world is sense experience. Corollaries: (1) an idea corresponds to a real object only if it is derived from or reducible to sense impressions, and (2) a term is meaningful only if it stands for a real object. 2

Hume on Meaning “When we entertain, therefore, any suspicion that a philosophical term is employed without any meaning…we need but enquire, from what impression is that supposed idea derived? And if it be impossible to assign any, that will confirm our suspicion.” 3

Logical Positivism Logical positivism maintains that the meaning of a statement is its method of verification. This is known as the verifiability theory of meaning. It follows that a sentence is meaningful only if it can be verified by sense experience. 4

The Argument from Logical Positivism to Logical Behaviorism 1.The meaning of a statement is its method of verification. 2.The way we verify claims about mental states is by observing behavior. 3.Therefore, what we mean when we say that someone is in a mental state is that they have a behavioral disposition. 5

Logical Behaviorism According to logical behaviorism, mental states are behavioral dispositions. A behavioral disposition is a tendency to behave in certain ways in certain circumstances. 6

The Argument from Ordinary Language to Logical Behaviorism Not all nouns refer to things, e.g., “waltz.” To dance a waltz is to dance in a certain way. Similarly, to have a mind is to behave in a certain way. 7

Thought Experiment: Ryle’s University Seeker “A foreigner visiting Oxford or Cambridge for the first time is shown a number of colleges, libraries, etc….He then adds, “But where is the University?” The visitor makes a category mistake in assuming that the University exists in the same way that the buildings exist. The same goes for dualists. 8

Qualitative Content To be in certain mental states, like pain, is to have a certain sort of feeling. The felt quality of mental states is known as their qualitative content. 9

Thought Experiment: The Perfect Pretender Imagine someone who cannot feel pain but nevertheless has learned to behave as if he or she can feel pain. This possibility shows that having the right behavioral dispositions is not a sufficient condition for being in pain. 10

Thought Experiment: Putnam’s Super-Spartans “Imagine a community of ‘super-Spartans’…They may, on occasion, admit that they feel pain, but always in pleasant, well- modulated voices…” This possibility shows that having the right behavioral dispositions is not a necessary condition for being in pain. 11

Putnam’s Argument Against Behaviorism 1.If having certain behavioral dispositions were a necessary condition for being in a certain mental state, then it would be impossible to be in that state and not have those dispositions. 2.But, as the example of the super-Spartans shows, it is possible to be in pain and not have the behavioral dispositions associated with pain. 3.Therefore, having certain behavioral dispositions is not a necessary condition for being in a certain mental state. 12

The Identity Theory According to the identity theory, mental states are brain states. It follows that anything that does not have a brain cannot have a mind. 13

Phineas Gage An explosion drove a steel bar through the head of Phineas Gage. He survived and recovered. However, his personality was radically different. Thus, what happened to Gage’s brain obviously affected his mind in a profound way. 14

Thought Probe: Mental Relay Stations Dualists do not believe that we think with our brains. So what is the function of the brain? To serve as a mental relay station between the mind and body? Have people with brain damage or Alzheimer’s disease suffered no cognitive impairment? 15

Identity and Indiscernability If two things are identical, then whatever is true of one must be true of the other and vice versa. So if mental states are identical to brain states, whatever is true of mental states must be true of brain states and vice versa. 16

Thought Experiment: Nagel’s Bat “I have said that the essence of the belief that bats have experience is that there is something that it is like to be a bat.” We can know everything there is to know about a bat’s brain without knowing what it’s like to be a bat. So mental states cannot be identical to brain states. 17

Nagel’s Argument 1.If mental states are identical to brain states, then it is possible to know everything about the mind by knowing everything there is to know about the brain. 2.But, as the example of the bat shows, it’s not possible to know everything about the mind by knowing everything about the brain. 3.Therefore, mental states are not brain states. 18

Thought Experiment: Lewis’s Pained Martian “…there might be a Martian who sometimes feels pain, just as we do, but whose pain differs greatly from ours in its physical realization.” This possibility shows that having a brain is not a necessary condition for being in a mental state. 19

Thought Experiment: Putnam’s Conscious Computer “It must be physically possible…to produce something with the same program [as the brain] but quite a different physical or chemical constitution.” This possibility shows that having a brain is not a necessary condition for having a mind. 20

Multiple Realizability What Lewis’s and Putnam’s thought experiments show is that minds can be realized in things other than brains. In other words, minds are “multiply realizable.” 21

Lewis’s and Putnam’s Arguments 1.If the identity theory were true, then it would be impossible for anything without a brain to have a mind. 2.But, as Lewis’s pained Martian and Putnam’s conscious computer show, things without brains can have minds. 3.So the identity theory is not true; having a brain is not a necessary condition for having a mind. 22

Thought Probe: Speciesism Suppose you fell in love with someone who seems to be the most intelligent, witty, and caring person you’ve ever met. Now suppose that “person” turns out to be an android. Would you conclude that he or she doesn’t have a mind? Would you still love him or her? 23

Thought Experiment: Searle’s Brain Replacement Imagine that your brain starts deteriorating and is gradually replaced by computer chips. One possibility is that your mind will be unaffected; another is that your mind will be destroyed but your behavior unaffected; a third is that you will be paralyzed but your mind unaffected. 24

Thought Probe: Neural Prostheses Suppose you had a failing brain and your only hope for survival was to have your neurons replaced by silicon chips. Would you do it? Suppose that those who’ve had it done report that they feel no different. Would you still do it? 25