Happy birthday, broseph. Hopefully I can help you avoid atoning for your shenanigans for at least one more day - it's what mentors are for.
So Kripke's Modal Argument and Chalmers' Zombie Argument both rely on the notion of possible worlds that we touched on last week, and they're both arguments against physicalism, the idea that everything can be described in terms of physical properties - if it's not physical, fuck it. It's not real. That's an interesting thesis for philosophers of mind, because it sure seems like consciousness isn't just physical. Descartes famously imagined himself as nothing but a mind - if everything physical ceased to exist, he said he could definitely keep thinking.
Kripke, a smart fucking bro indeed, invented the notion of rigid and accidental designators. Rigid designators always refer to the same thing in every possible world where that thing exists. So 'Bill Clinton' is a rigid designator. We can construct a possible world in which he knows what the definition of 'is' is, and a possible world in which he gets away with everything like a boss, and a possible world in which he makes his fame on Sesame Street instead of as a politician. But in all the worlds, it's still Bill motherfucking Clinton.
Accidental designators, by contrast, pick out different things in different worlds. 'My humble
That seems pretty strong. If 'Philosophy Bro' always names the same guy and '[NAME REDACTED]' always names the same guy, then if Philosophy Bro and [NAME REDACTED] are the same guy in one world, they have to be the same guy in every world where he exists. Otherwise they're not the same asshole in any world. Same thing with pain and a neuron firing.
But are we sure what exactly 'my pain' is? What if there's a world where we all feel pain by hearing Sarah Palin's voice in our left ear? It's still excruciating, but in a different way. What are the essential properties of pain? Kripke seems to rely on a notion of pain necessarily being the way we actually experience it. Maybe there's a world in which we 'feel' pain but don't particularly dislike it, or are even bothered by it - would anyone know that we're in pain, even though the relevant physical states obtain? How do we know 'I'm not feeling pain' is true instead of 'I'm not bothered at all by pain because I'm a fucking champion' or 'I experience pain the same way I experience silence' is true? It looks like successful attacks on the position will attack the idea that it is in fact possible to have one without the other.
On the flip side of the coin, Chalmers' Zombie argument also uses possible worlds to argue against physicalism. He doesn't mean zombie in the classical brain-eating tradition, and a philosophical zombie isn't just a zombie that wonders about the right to not to have one's brain eaten. A philosophical zombie is a person that walks, talks, acts and responds just like a human being, but who has no experience of consciousness whatsoever. Yeah, if you double-tap him with a shotgun, he's going to scream in pain, because that's what normal people do, but he doesn't actually feel pain - he's just going through the motions, like bros when they call you the next morning or celebrities when they enter rehab.
Now, what if you had a possible world in which everyone was a zombie, but everything else was exactly the same? I still write this blog, you still do whatever it is you do, and Lindsay Lohan still cries in court, but no one has any consciousness. We're all just going through the motions. If that's possible, then physicalism is false, because all the physical facts are the same but no one has consciousness - so consciousness must be something else, something non-physical.
Some problems - first, how would we know a zombie? "Hey, bro, you a zombie?" "What? No, I'm Catholic." That's exactly what a zombie would say. Ludwig Wittgenstein argued in the Philosophical Investigations that we all talk about pain, and we all act like our pain is the same, even though we can't ever experience each other's pain. Imagine everyone kept a small box with them - in my box is a beetle. I've never seen what is inside anyone else's box, but they all describe a beetle just like mine; on what grounds can I doubt them? it doesn't really make sense to question their beetle, since I can't ever get in their box - pain is the same way. If a zombie had an empty box, how the fuck would we ever know? He talks about pain the same way we do.
But more importantly, what does it mean for a zombie not to have pain? Well, if physicalism is true, it just means for the relevant brain states to not obtain. So perhaps Chalmers' is begging the question. He claims that there's no inherent contradiction in the possible zombie world, but there is if the the following two theses are both true: physicalism is true and zombies don't feel pain but have all the same brain states as their 'normal' counterparts - if they have the same brain states and physicalism is true, they feel pain. So Chalmers may have to assume physicalism is false to show physicalism is false.
We also have problems imagining what it's like for a zombie to not have pain but have the same physical states. Peter van Inwagen in his essay "Modal Epistemology" laid out modal skepticism, they idea that we've gone way too fucking far with our 'modal intuitions'. He might say something like "Philosophical zombies? Really? How the fuck would that even work? Look, when you endorse a possible world, you endorse an entire universe that has to be consistent. I'm not saying you have to picture its endless boundaries and everything in between, but you do need to be able to show that 'they don't feel pain' is true, and not something else like 'I can't tell if they feel pain.' If the brain states aren't different and they act like they're in pain, how can you be sure?"
Of course, these objections revolve around rejecting the notion of the zombie, and a successful attack will show some incoherence like those noted above. If Chalmers can successfully defend that the idea of a zombie is consistent without question-begging, that's game set match, bitches.
Modal arguments (arguments that use possible worlds) are useful in discussing how the world could have been and what needs to be, but, as with the modal ontological argument, whenever there is a controversial modal premise involved, red flags shoot the fuck up. Sometimes it's hard to show that something batshit off-the-wall crazy is possible unless one already believes it's possible - some modal arguments look obviously right to their supporters and "are-you-fucking-kidding-me" wrong to their detractors.
On the other hand, they do help us consider things like emergent properties that we can't directly observe - maybe Chalmers and Kripke are both right. It's hard to say conclusively. The relevant bros are all pretty fucking smart, and I think that's an important role of modal arguments: they help establish important doubts about what we take for granted.
Saul Kripke lays out his modal argument and many others in his watershed Naming and Necessity; David Chalmers 'fleshes out' the idea of a philosophical zombie in The Conscious Mind.
You can read Peter van Inwagen's excellent essay Modal Epistemology online for free if you have JSTOR access.
If you haven't read Wittgenstein's Philosophical Investigations, well... fix it.
Wikipedia has a page on Philosophical zombies; So does the SEP.
For the second week in a row, I have a relevant shirt. Actually, my most popular one. Coincidence! I swear.