So what Putnam was pointing to was that, instead of thinking about what psychological states are made of, whether they're made of human brain stuff or alien brain stuff. We should be thinking about what psychological states do. Now, in order to get our heads around this idea, let's take another detour. Imagine travelling to a country where instead of notes and coins, people trade using shells they use the shells to pay for services, the shells rise and fall in value dependent on market forces and people save shells for a rainy day. The shells function in just the same way as bits of metal and paper function as currency in our society even though they are made of quite different things. Or imagine that you go someplace where people trade using livestock swapping cows for other goods or services. Cows, shells, bits of metal and paper are all very different to look at and have nothing in common in terms of what they're made of But they all share a function. They can be traded for goods and services. They have value that can fluctuate dependent on market forces. And one can judge another's wealth by how many tokens of cows, shells, or bits of metal and paper one has. Let's take a different example. Imagine lots of different chairs. What makes all of these pictures that we see, chairs? Well, is that they function as chairs, we can all use them for sitting down on and sitting down in such a way that we're raised up from the floor. What allows us to say that all these things here are chairs, is that they function in a particular way, they function so as to allow sitting. Now, this has ties back to the problem that Putnam was pointing out with identity theory. He's saying we shouldn't identify mental states of what they're made of, just as we shouldn't identify a chair with what it's made of. Because as you can see, chairs can be made of totally different things. Money can be made of totally different things. What allows us to say that all these things are chairs and all these things count as money, is what they do. And that's exactly what Putnam thought we should do with psychological states. So instead of saying, what makes a particular psychological state what it is? What makes my thought about Paris, about Paris is what it's made of, the particular mixture of chemicals and hormones. Putnam says, that instead, we should think about what that psychological state does, how that psychological state functions? And in this way, if we think about how pain functions, so we can think about pain as a particular state that functions to makes us wince when we touch something. Maybe to say aw or to pull a face. If we think about how pain functions, then we can then see how pain can be realized in different species. How we can see pain in humans and pain in octopi, even though pain in humans and pain in octopi is made up of very different stuff. It's made up of octopus brain stuff in one instance and human brain stuff in the other. What it's made of doesn't matter. What is crucial is how it functions. This is the materialist view know as functionalism, it says that we should tell mental states apart. We should think about mental states, not by what they are made of, but by what they do. So what is it that mental states do? Well, the first thing that mental states do is they cause particular behaviors. So, as, the example I like to use is that, if I want some chocolate, then that particular psychological state causes me to engage in particular behaviors to finally coat and go out to go to the shops. But they do other things as well, they can cause new psychological states. So if I want chocolate, this could also cause a desire for me to find my coat and I think mm, I really want some chocolate. Okay. Till you get some more chocolate, then I should go find my coat. Alright. Let's go find my coat. So that I have taken a psychological state in my desire for chocolate which causes a new psychological state in me. The other important thing to understand about psychological states or mental states is that they're caused by particular things as well. So my desire for chocolate might be caused by the smell of chocolate. I could be walking down the street, for instance, and smell the chocolate coming out of the patisserie and think mm, chocolate, I really want some. So, that particular perception of the world caused me to go into a particular state, that oh, I really want some chocolate. Which then cause me to go into particular behaviors, i.e., maybe walking in to the shop or thinking, do I have enough money for some chocolate? Oh, I'm not sure. Oh, I'm going to eat later. I probably shouldn't have some chocolate. So, psychological states cause a function in this particular way. They're caused by sensory inputs and in turn they cause behaviors, and psychological states, other internal states as their outputs. The other thing that can cause a psychological state is another psychological state. So, I might have the belief that I'm hungry, that's a particular mental state that I have, and that causes me to desire chocolate. So you can have psychological states that cause other psychological states. Now, this is the idea of functionalism. This is the idea that in order to understand what the desire for chocolate is, we have to understand it in terms of its functional role. So the desire for chocolate might cause me to put on my coat, go out to the shops. In contrast, my belief that there's chocolate in the fridge will cause a whole different set of behaviors in psychological states. Might cause me to get up and go to the fridge, it might cause me to answer, yes, if someone says to me, hey, is there any chocolate in the fridge? And this is the point that Putnam is trying to drive at. He's saying that we should understand psychological states not by what they're made of, but how they function. The types of behaviors and psychological states that they cause and the types of sensory inputs, and perceptions, and psychological states, which cause them. So, this is how I can see that my desire for chocolate is different from my belief that there is chocolate in the fridge. Because it's caused by different things, my desire for chocolate is caused by the smell of chocolate and the belief that I'm hungry. And it causes different behavior, such as going to the shops, and trying to find my coat, and that's very different form the belief that there's chocolate in the fridge. Because the belief that there's chocolate in the fridge is caused itself by a whole different set of sensory inputs. It's caused perhaps by my perception that there's chocolate in the fridge or someone telling me, hey, there is chocolate in the fridge. And that mental state function serves to cause very different behaviors causing me to go to the fridge if I want some chocolate. Now, you can see how we've completely stepped away from what psychological states are made of. We've totally stepped away from this mix of chemicals, mix of hormones, or octopus brain, or alien stuff. We've abstracted away and saying no. What we should be looking at, what the fundamental feature of a psychological state is, is what it does. And what allows us to attribute a state like pain to an octopus, is if that octopus functions in such a way that we can say it's in the state of having pain. So if the octopus touched something that was burning, and shrank away very quickly, we could say, oh, now octopus is in a particular state that causes it to shrink away when it touches something hot. Well, maybe that octopus is in a state of pain because that, that state of pain functions in humans, certainly, to have withdrawal behavior when you touch something hot. Stating to use the same types of behaviors in an octopus, then that would suggest that the octopus can also have pain because it's in a state that's functioning in exactly the same way as human pain. So again we've stepped away from what it's made of and we're looking at what states do.
