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'The possibility of Martians with a completely different physiology but a mental life just like ours shows that mental states cannot be brain states' Discuss. In this essay, I want to argue that the possibility of Martians, with a completely different physiology, but a mental life just like ours does not show that mental states are not brain states. I will argue that a particular, tweaked, version of functionalism allows for mental states to be the cause of a being's behaviour, whatever its physiological make-up. I will start by outlining Lewis' argument. He separates two different thought experiments concerning pain. Firstly, suppose there is a man of the same physiology as a normal human, and who feels pain just as we do - i.e. through the same electrical impulses along the same nerves etc -but that rather than feeling it when hit on the head, or poked in the belly etc. he feels it simply when jogging on an empty stomach. Further, rather than distracting him as it would you or I, the pain itself just makes him concentrate harder on the exercise. Neither does it make him groan or writhe about on the floor in pain. Suppose that in place of this he simply does a funny little jig and smiles. Crucially, he is, therefore, not motivated to rid himself of this 'pain'. In searching for a coherent theory of mind, it is often suggested, we must account for both this kind of pain, and that which is more common to you or I. He calls this 'mad pain'. Secondly, Lewis outlines the scenario of 'Martian pain'. This is pain has the same effect on the Martian as it would on a human. The Martians react by groaning and writhing about (in extreme cases), they are always motivated to avoid it, and will struggle to free themselves of it in instances of its occurrence. However, their physical makeup is almost completely different to that of humans. They have no neurons/nerve endings etc., they have a completely different brain altogether, and, in contrast to humans, the event of pain is not accompanied by the firing of (what are known as) "c-fibres" in their heads. In fact, something else altogether happens. For the sake of argument, let's say that a bubble inflates in their left pectoral, and passes into their right. It is claimed that a credible theory of mind will have to account for this type of pain also. So Lewis needs a theory that takes both causal roles and physical processes as contingent. This all begs an enquiry into the relation between our mental states and subsequent bodily movements or reactions. It seems plausible to suggest that there is some causal influence of the mind on the body. Furthermore, although it would be quite beyond the scope of this essay to discuss in detail my reasons, I will take it for our present purposes that all physical events have physical causes. From the conjunction of these two ideas, we get the conclusion that all mental events of both types are identical with physical states or events. Theories that assert this are called identity theories. By this, the mere fact that pain does not appear like the firing of a nerve does not rule out that that is what it is. Hume raises a difficulty here. In cases of sensational mental events e.g. pain, we are supposed to be able to identify it with some kind of neural event. But, in practice, it is difficult to locate that event. If I get kicked in the stomach it is hard to see what event is the pain itself. One might say it is simply the firing of the nerves in my stomach, but supposing the nerve had been redirected, I might not have felt anything at all. Surely we would not want to go on saying that it was pain, if I hadn't felt anything. Furthermore, consider the phenomenon of sight. Is there any reason to locate the mental event of seeing a Winnebago on a particular part of my eye rather than on the Winnebago itself?
So it seems arbitrary to identify pain, for instance, with the firing of the nerves rather than with any other causes of the sensations. A credible identity theory, therefore, will have to argue that sensational mental events take place in the brain itself. In other words, to relate back to the question, a credible identity theory must maintain that mental states are brain states.
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