Philosophy

Ted and Robot Ted

Here’s an example to help generate the intuition behind functionalism. Consider Ted, who is something of a klutz and cuts his finger on a tack, and grits his teeth, sheds a tear, and lets out an “Ouch!” as a result. All materialists would say that what is going on here is a purely physical series of causes and effects. The skin is torn by the tack, nerve endings register this damage and send signals to the spinal cord, a reflex response pulls the arm back, further signals are sent to the brain, clusters of neurons fire, these cause others to fire, which in turn causes muscles to flex so that the teeth clench, a tear is shed, and a yelp is generated by the larynx. Along the way, there are mental states involved – a sensation of pain, a feeling of worry, a thought about where the Band-Aids are – but all of that is in some way identical to part of the pattern of physical causes and effects.

Now imagine a second individual who, from the outside, looks and acts exactly like Ted. You’d be sure it was him if you met him. However, this individual is in fact a robotic duplicate of Ted. He is made of artificial parts – artificial muscles, artificial nerve endings, artificial light-sensitive receptors for eyes, microchips in place of neurons, and so on. However, all these parts function the way human body parts do. An artificial heart pumps blood just like a real one does. And Robot Ted’s artificial nerve endings register heat, cold, pressure, and damage just the way real nerve endings do; his artificial eyes detect light just like real eyes do; and so on.

In particular, his artificial neurons do what real neurons do. A neuron is, after all, a kind of signaling device. It gets signals from other neurons, and sends them to yet others. The microchips that make up Robot Ted’s brain do that, and they do it in a pattern that exactly parallels the firing patterns between the neurons in human Ted’s brain. Hence, just like human Ted, when Robot Ted cuts his finger on a tack, he grits his teeth, sheds a tear, and lets out an “Ouch!” as a result. Indeed, in every other way too he acts exactly like Ted. Again, imagine that he’s so realistic that you’d think it was Ted.

Which one is the real Ted? Even Bill doesn’t know.

Now, the question is: Does Robot Ted also have mental states – sensations, emotions, thoughts, etc. – the way that Ted does? The functionalist says: Yes, he does. It’s true that Robot Ted is made of artificial parts, but (the functionalist argues) that doesn’t matter. If an artificial heart can pump blood and an artificial muscle can flex, why can’t a set of artificial neurons generate a mind? It’s also true that the artificial parts are entirely material, but so are human Ted’s real body parts, including his brain. And for a materialist, purely physical components can generate a mind as long as they are put together the right way. So why should it matter whether those components are artificial?

What does matter, the functionalist says, is how the parts function. If something functions to pump blood, then it’s a heart, even if it’s made of artificial materials. If something flexes the way a muscle does, then it’s a muscle, even if it’s made of artificial materials. And if something functions the way a system of neurons do, then it will generate a mind just as (according to materialists in general) real neurons do.

An alternative to the identity theory

What matters to having a mind then, is how you function, not what you’re made out of. Lots of things are like this. For example, a knife is defined in terms of its function. If something is a hand-held single-bladed instrument used to cut things, then it’s a knife, and it doesn’t matter whether it’s made out of stainless steel, or plastic (as a disposable picnic knife might be), or glass (as a decorative wedding cake knife might be).

Similarly, if something going on inside a physical system, whether a human body or a robot, functions to get the system from damage (as a kind of input to the system), to yelping, flinching, and the like (as outputs from the system), then that something just is a sensation of pain; if something functions to get the system from light from raindrops striking its visual receptors (as input) to behavior like going to get an umbrella (as an output), then that something just is the belief that it is raining; and so on for other thoughts, sensations, and mental states in general.

On this view, any system of causes and effects that functions in these ways will count as having a mind. And it doesn’t matter whether it is neurons, computer chips, or whatever that is performing these functions. The problem with the identity theory, according to functionalism, is that it focuses too exclusively on the brain. For the brain is just one of several possible physical systems that might in theory have a mind. As long as it exhibits the right pattern of causes and effects, many various kinds of systems – made out of neurons, or computer chips, or some silicon-based extraterrestrial organic material – might in theory have minds.

So, the right thing to say is not that the mind = the brain per se. That’s like saying that a knife = a kind of stainless steel object. It’s too narrow. The right thing to say is that the mind is identical to an abstract system of causes and effects that could exist either in a brain or in some other possible kinds of system. Function is what matters. Functionalism, developed by thinkers like Hilary Putnam, develops this insight into an alternative theory of the mind.

Hilary Putnam (1926-2016)

More formally, the view can be defined as follows:

Functionalism: Holds that a mental state or process is to be analyzed in terms of its functional role, i.e. the set of causal relations it bears to (1) those environmental inputs to the body that typically generate it, (2) the behavioral tendencies it in turn tends to generate as output, and (3) the other mental states it is typically associated with.

For example, a sensation of pain can be defined as follows:

pain = that state which (1) typically results from bodily injury as the input, (2) tends to cause outputs like crying out, flinching, nursing of the injured area, etc., and (3)

is typically associated with distress, practical reasoning aimed at relief, etc.

And so on for other types of mental state – the belief that it is raining, the belief that it is sunny, the desire to eat pizza, the fear that you’ll fail the final exam, the memory of grandma’s house, and so on. Each mental state can be defined in terms of how it functions to get the system (such as the body) from certain causal inputs to the body to certain outputs in speech, behavior, and the like. A mind is just a system of mental states with these various functions.

Pain performing its function.

Notice that this is similar to J. J. C. Smart’s “topic-neutral” analysis (which we talked about last week), because it says that we can describe what a mental state is in a way that is neutral about what exactly it is that it is made out of. The difference is that Smart saw his analysis as a way to defend the identity theory, whereas the functionalist says that if we follow it out consistently we’ll see that it really gives us an alternative to the identity theory.

Advantages and implications

The dispute between identity theory and functionalism is basically an argument between members of the same materialist family. Functionalists claim that if you accept the general materialist worldview, it is preferable to adopt their position rather than the identity theory.

For example, they say that functionalism can better explain what they call the “multiple realizability” of the mind than the identity theory can. Recall from last time that even some identity theorists (namely “token identity theorists”) admit that there is not a tight one-to-one matchup between types of mental state on the one hand, and types of brain state on the other. The relationship is messier, like the relationship between having $20 and having a certain kind of currency. Sometimes having $20 involves having a twenty dollar bill, sometimes it involves having a bag of coins, and sometimes it involves having $20 in the bank, as an electronic record in the bank’s computer system.

Similarly, sometimes having a sensation of pain or the belief that it is raining involves having a certain specific kind of brain state, but sometimes it might be associated with another kind of brain state. And sometimes it might involve no brain state at all, but rather the passing of electrical current between computer chips, as in Robot Ted. The mind is therefore multiply realizable – it can be realized in, or come to exist in, multiple kinds of physical system.

This would be odd if the mind was identical to the brain, specifically. But it is not odd if the mind is instead identical with an abstract system of causes and effects which could exist either in a brain or in some other kind of system that functions in a similar way.

Now, one application of functionalism is the idea that the specific kind of abstract system of causes and effects that we can identify a mind with is the kind we call the program that a computer is running. Functionalism thus opens the door to the thesis that the mind is a kind of software, and the brain is the hardware that is running the software. This is sometimes known as computationalism, and these days it is the best-known and most popular way of spelling out a materialist theory of the mind. We’ll look at it in more detail next week.

“Cogito, ergo sum!”

In the meantime, here are some optional YouTube videos summarizing the basic idea of functionalism and relating it to other versions of materialism. The first three are very brief, and the last two are more in-depth:

John Searle on Behaviorism, Identity Theory, and Functionalism: