Minds and Machines Summer 2011 Monday, 07/11

Logistics Last week’s PP Slides now on-line. Quiz: overall happy with it. Everyone who turned in a Quiz passed. Some comments: 1. Use Examples! 2. Behaviorism is a materialist theory. 3. Behaviorism is not just about our ways of thinking of mental states. Movie: Blade-Runner this Thursday. Today we’ll start talking about Functionalism in some detail. The contrast should also help clarify the other two theories we’ve looked at so far.

Prelude: Zen & The Art of Motorcycle Maintenance

Prelude: Zen & The Art of Motorcycle Maintenance “That's all the motorcycle is, a system of concepts worked out in steel. There's no part in it, no shape in it, that is not out of someone's mind. I've noticed that people who have never worked with steel have trouble seeing this...that the motorcycle is primarily a mental phenomenon. They associate metal with given shapes...pipes, rods, girders, tools, parts...all of them fixed and inviolable, and think of it as primarily physical…John looks at the motorcycle and he sees steel in various shapes and has negative feelings about these steel shapes and turns off the whole thing. I look at the shapes of the steel now and I see ideas. He thinks I'm working on parts. I'm working on concepts.” (Robert Pirsig)

Prelude: Zen & The Art of Motorcycle Maintenance What could this possibly mean? In what sense is a motorcycle a “mental phenomenon”? Isn’t it a paradigm of a physical item? It can’t be that the bike is mental because it’s made by human beings. And it would be loony to claim that it’s made out of mind-stuff. So is Pirsig a loony or just confused?

Prelude: Zen & The Art of Motorcycle Maintenance Let’s look at one part of a bike, the engine. Pirsig’s friend, John, thinks of an engine as just a certain type of construction made of steel that’s built out of certain parts of a particular shape (e.g. pipes, rods, etc.). John is an Identity Theorist about engines. He thinks there is some specific set of physical properties that all engines have in common. Anything that doesn’t have these properties (e.g. parts, shape, etc.) would not count as an engine by John’s lights.

Prelude: Zen & The Art of Motorcycle Maintenance But Pirsig seems to have hit on an important insight about artifacts. The idea/concept of an engine does not specify how an engine might be designed and built—whether it uses gasoline, electricity or bio-fuels, whether it is a piston or rotary engine, how many cylinders it has, whether it uses a carburetor or fuel injection, etc.

Prelude: Zen & The Art of Motorcycle Maintenance The concept of an engine is defined by a job description, or causal role, not a description of mechanisms that execute the job. As long as a device is capable of transforming energy into motion, it counts as an engine. If a device meets the job-description but involves a team of angels blowing cool air into a cylinder, that device would count as an engine all the same.

Prelude: Zen & The Art of Motorcycle Maintenance The different parts of the bike (and consequently a bike itself) may be realized in all sorts of radically different ways. When John is looking at a part of a bike, he just sees the particular realization of that part of the bike. When Pirsig looks at the part, he sees something more abstract, something that can be realized in all sorts of radically different ways. That’s why he says that he’s not working with parts, but is working with concepts.

Prelude: Zen & The Art of Motorcycle Maintenance Concepts of other artifacts and many biological concepts are similar. What makes an organ a heart is the fact that it pumps blood. The human heart may physically differ from hearts in reptiles or birds. But these all count as hearts because of the job they do in the organism. A mechanical heart would still count as a heart as long as it meets the abstract job description for a heart.

Functionalism Claims: Like concepts of artifacts & biological concepts, mental concepts carry no constraint on the actual physical-biological mechanisms that realize or implement them. Our concepts of mental states are defined by their job descriptions or causal roles. For example, the concept pain is defined by the job-description “tissue-damage detector”.

Functionalism Like Behaviorism, Functionalism can be a thesis about both our concepts of mental states and about the mental states themselves. F is a functional property (or kind) just in case F can be characterized by a definition of the following form: For something x to have F =def for x to have some property P such that C(P), where C(P) is a specification of the job description or causal work that P is supposed to do in x.

Functionalism For example, the property of being a mousetrap is a functional property because it can be given the following functional definition: x is a mousetrap =def x has some property P such that P enables x to trap and hold or kill mice. Just like with engines or pain, there are indefinitely many “realizers” of the property of being a mousetrap.

Functionalism Functional properties (e.g. being a mouse-trap) are “second-order” properties that can be realized or implemented by “first-order” properties (e.g. being a specific kind of physical device). Property Q realizes functional property F in system x just in case C(Q), that is, Q fits the job-description C in x.

Functionalism On its own, functionalism is compatible with dualism. It allows that a mental state such as pain could be realized in a non-physical way. But many functionalists wanted to place constraints on possible realizations of mental states. One example of such constraint is realization physicalism. Notice that the latter is no longer a thesis about our concepts of mental states but a metaphysical thesis about the mental states themselves.

Functionalism vs. Behaviorism and the Identity Theory One good way to understand the difference between these views is to see how each of them answers the question: What do all mental states of a particular psychological kind (e.g. all pains) have in common in virtue of which they fall under the same psychological kind?

Functionalism vs. Behaviorism and the Identity Theory The Identity Theorist answers: what all pains have in common that makes them instances of pain is a certain neurobiological property, namely, being an instance of C-fiber excitation. This is because mental kinds (e.g. pains) are just physical kinds (e.g. C-fibers firings).

Functionalism vs. Behaviorism and the Identity Theory The Behaviorist answers: What all pains have in common is a certain behavioral property. Two organisms are both in pain just in case they are disposed to exhibit the behavior patterns characteristic of pain (e.g. escape behavior, withdrawal behavior, and so on). This is because, for the Behaviorist, mental kinds (e.g. pains) are just behavioral kinds (e.g. tendencies to groan, wince, escape, etc.).

Functionalism vs. Behaviorism and the Identity Theory The Functionalist answers: what all pains have in common that makes them instances of pain is that they meet the job description of being “tissue-damage detectors”. Compare: what makes something a mousetrap, a carburetor, or a thermometer is its ability to perform a certain function, not any specific physical/chemical structure or mechanism.

Functionalism vs. Behaviorism Behaviorism identifies mental states with behavior and behavioral dispositions. Functionalism identifies mental states with real internal states that can cause behavior & behavioral dispositions as well as other mental states. For the behaviorist, to be in pain is to be disposed to wince and groan. For the functionalist, it is to be in an internal state that causes winces and groans.

Motivations for Functionalism One problem for the identity theorist was that pain might turn out to be correlated with different brain processes in different creatures. One response that some of you raised was to introduce different notions, like “pain-in-humans” and “pain-in-octopus” and so on, but to reject talk of “pain-in-general”. But there’s a strong intuition that pain is a mental state that we might share with other creatures.

Motivations for Functionalism One problem for the behaviorist was that there seems to be no such thing as the distinctive behavior associated with a single mental state. The functionalist has systematic ways to describe the connection between any one mental state and all the other mental states in a creature’s psychology. We’ll be looking at two such ways in the next couple of days.

Machine Functionalism Many functionalists have thought about the mind in analogy with the operations of a computing machine. They tried to understand the mind as a software – a sophisticated job description– run on the hardware of the brain. On this view, we should expect mental states to be multiply realizable. Consider the following computers that may run the same (simple) software.

For Tomorrow We’ll look into Machine Functionalism in much more detail. Read Putnam’s short article “The Nature of Mental States”. I highly recommend reading the section on Turing Machines from Kim’s chapter before tomorrow’s class.