Yeah, this is basically right. Putnam was defending externalism about mental content, the idea that the content of our mental representations isn’t fully determined by intrinsic facts about our brains. The twin earth thought experiment was meant to be an illustration of how two people could be in identical brain states yet be representing different things. In order to fully determine the content of my mental states, you need to take account of my environment and the way in which I’m related to it.
Another crazy thought experiment meant to illustrate semantic externalism: Suppose a flash of lightning strikes a distant swamp and by coincidence leads to the creation of a swampman who is a molecule-for-molecule duplicate of me. By hypothesis, the swampman has the exact same brain states as I do. But does the swampman have the same beliefs as I do? Semantic externalists would say no. I have a belief that my mother is an editor. Swampman cannot have this belief because there is no appropriate causal connection between himself and my mother. Sure he has the same brain state that instantiates this belief in my head. But what gives the belief in my head its content, what makes it a belief about my mother, is the causal history of this brain state, a causal history swampman doesn’t share.
Putnam was not really arguing against the view that “the meanings in our heads don’t have to refer to anything in the world”. He was arguing against what he called “magic theories of reference”, theories of reference according to which the content of a representation is intrinsic to that representation. For instance, a magic theory of reference would say that swampman does have a belief about my mother, since his brain state is identical to mine. Or if an ant just happens to walk around on a beach in such a manner that it produces a trail we would recognize as a likeness of Winston Churchill, then that is in fact a representation of Churchill, irrespective of the fact that the ant has never heard of Churchill and does not have the cognitive wherewithal to intentionally represent him even if it had heard of him.
Yeah, this is basically right. Putnam was defending externalism about mental content, the idea that the content of our mental representations isn’t fully determined by intrinsic facts about our brains. The twin earth thought experiment was meant to be an illustration of how two people could be in identical brain states yet be representing different things. In order to fully determine the content of my mental states, you need to take account of my environment and the way in which I’m related to it.
Another crazy thought experiment meant to illustrate semantic externalism: Suppose a flash of lightning strikes a distant swamp and by coincidence leads to the creation of a swampman who is a molecule-for-molecule duplicate of me. By hypothesis, the swampman has the exact same brain states as I do. But does the swampman have the same beliefs as I do? Semantic externalists would say no. I have a belief that my mother is an editor. Swampman cannot have this belief because there is no appropriate causal connection between himself and my mother. Sure he has the same brain state that instantiates this belief in my head. But what gives the belief in my head its content, what makes it a belief about my mother, is the causal history of this brain state, a causal history swampman doesn’t share.
Putnam was not really arguing against the view that “the meanings in our heads don’t have to refer to anything in the world”. He was arguing against what he called “magic theories of reference”, theories of reference according to which the content of a representation is intrinsic to that representation. For instance, a magic theory of reference would say that swampman does have a belief about my mother, since his brain state is identical to mine. Or if an ant just happens to walk around on a beach in such a manner that it produces a trail we would recognize as a likeness of Winston Churchill, then that is in fact a representation of Churchill, irrespective of the fact that the ant has never heard of Churchill and does not have the cognitive wherewithal to intentionally represent him even if it had heard of him.