David Lewis' Improvement of Functionalism

David Lewis and the Hydraulic Brain.  Lewis proposes an improvement on functionalist theory.  He first identifies a problem with functionalism regarding multiple realization and proposes a solution to this problem.  Imagine a martian and human madman.  The martian acts just like us but it has a mechanical, hydraulic brain. Even though the martian has the same pain and has the same kinds of behaviors as humans have it, the physical states that cause the pain and cause the subsequent behaviors are different.  Now, imagine the madman.  The madman has all the same physical systems that normal humans have and he feels pain, but it is caused by different things and he reacts to it in a very different way.  His pain is not caused by cuts, punches and falls.  Rather, he pain is caused by light exercise on an empty stomach.  Also,  instead of groaing, screaming and using an icepack, he may think about math or cross his legs and snap his fingers. The madman is in pain but he neither exhibits behaviors that are typical pain behaviors for humans nor is his pain caused by the same conditions.

Here is the problem: Functionalism says that pain is a functional states.  On the one hand, the purpose of the functional state of pain is the same for us and the martian but it is different for us and the madman.  On the other hand, the physical brain state is the same for us and the madman but it is different for us and the martian.  Putnam’s version of functionalism can explain the martian’s pain but cannot explain the madman’s pain.

Lewis comes up with a version that can explain both the martian’s pain and the madman’s pain.   Lewis says that we must allow for different behaviors to be typical for different organisms or different populations who have the same mental state.  We must allow that there will be different sets of behavioral dispositions associated with mental states in different populations.  For example, in a population of normal humans, pain is associated with the behaviors of crying, yelling and cursing.  In a population of Buddhist monks, however, pain is associated with behaviors of maintaining physical composure.  The madman is so unique that he does not belong to our population.  This is why it is not a problem that his behavior differs so much from the behaviors that are typical to the human population.

Lewis' improvement means that (1) different organisms or different populations of people can have different behaviors associated with mental states that they share with us and (2) people who are as unique as the madman are not counterexamples for functionalism because they are not members of our population.

Sven noted that there may be a problem with defining a population.  Certainly we cannot give a species or biological definition because then the madman is a problem for functionalists still.  We can give a cultural definition, however.  For example, the set of behavioral dispositions associated with pain will be very different in the cultures of Buddhist monks, professional wrestlers and suburban Californians.  Likewise, the behavioral dispositions for love will differ between Mormons in the U.S. and native tribes in Africa.