What are Possible Worlds?

these days in the philosophy of language there's a lot of talk about possible worlds so I'm going to explain what those are and one of the most famous instances in which the idea of possible worlds comes up is in Saul ky's famous lectures and then book naming in necessity where he talks about rigid designators and non- rigid designators so I'm going to explain those as well the first thing to clarify is just about the word world sometimes we use the word world to mean plan like Earth is a different world from Mars and Jupiter or whatever that's not how philosophers are using the word world here they're using the word world to talk about the whole universe a whole possible way that the Universe could be on this way of using the word world the moons of Jupiter are just as much a part of our world as like New Jersey is so in our world things are a certain way Mount Everest is the tallest mountain on Earth that's how it is is in our world but there were other possibilities things could have gone differently Mount Everest is part of the Himalayan Mountains and that mountain range was formed when the Indian subcontinent collided with Eurasia another possibility is that things went differently maybe the Indian subcontinent moved in a different direction this is like millions or billions of years ago or whatever if that had happened then Mount Everest never would have formed maybe India would have collided with Australia instead and uh there would have been some other smaller mountains or whatever formed but there never would have been a Mount Everest the way that we talk about this is that there's different possible worlds there's the actual world where India crashed into Eurasia thrust up the Himalayan Mountains and then there was this mountain it got called Mount Everest and it's the tallest one baby cut out the baby obviously but there are other possible worlds in one of those other possible worlds let's suppose a kagua which is in the Argentine Andes is actually the tallest mountain because now it doesn't have to compete with the Himalayas because the Himalayas never formed in that possible World I'll give you one more example LeBron James won the 2016 NBA Finals but he kind of got lucky you know what happened was that in game four Draymond Green who played for the Golden State Warriors got in some kind of altercation or something like that and he got suspended for game five and because he wasn't playing in game five LeBron and the Cavaliers won game five and then they went on to win the championship that's how it went in the actual world but there are other possible worlds where Draymond keeps his composure in game four doesn't get suspended for game five and then the Warriors win in game five which would mean probably that Kevin Durant doesn't sign with the Warriors in like 2017 or whatever like things go real crazy okay so you get the idea there's all these possible worlds they don't actually exist anywhere in space or whatever they're just something that we imagine unless you're David Lewis he was a famous philosopher he thought that they actually exist we're not going to talk about him right now philosophers often talk about some possible worlds being closer to other possible worlds or more distant I've drawn here this beautiful diagram I use the at symbol to mean the actual possible world and then let's say this B here this is the possible world where LeBron James does not win the 2016 NBA finals this is just a metaphor right like these worlds don't exist in space so they can't be next to each other or anything like this this is this is purely met orical but here's the thing that alternative reality in which Draymond Green keeps his composure doesn't get suspended and LeBron doesn't win the 2016 finals that alternative reality is like all things considered pretty similar to ours it's similar so we draw it closely like it's closer this other world in which India doesn't collide with Eurasia like hundreds of millions of years ago or whatever that world is massively different like maybe humans never even evolve in that world if humans never even evolved well that's more different than our actual world than the one where LeBron just didn't win this one championship and so we draw that world farther away and we say metaphorically that it is a more distant possible World here's where things get interesting we can use our words our terms in the English language or in any language to talk about these alternative realities like we do it all the time I've been doing it in this video I said something like in this world LeBron James didn't win the 2016 NBA championship well there I did it I used this name in English in our world to talk about some guy in another world and we can do this with things other than names we can do it with descriptions as well take for example the description the 2016 NBA Finals MVP that expression here in our world in this video right now that expression refers to LeBron LeBron James in the actual world but in this possible world that's not actual it refers let's suppose to Steph Curry because if the Warriors had won that year then Steph probably would have gotten Finals MVP okay now notice something about these names LeBron James the name LeBron James refers to the same guy in all the possible worlds where he exists in the actual world the name LeBron James refers to LeBron James in this possible world the name LeBron James refers to LeBron James in this possible world the name LeBron James refers to no one because there are no humans in that world because humans never evolved let's say so in every world where LeBron exists this name refers to the same guy it refers sort of rigidly it like sticks to that same guy in a rigid way that's what a rigid designator is according to Saul kryy proper names are rigid designators they designate or refer to or pick out the very same person in all the possible Worlds at least all the possible worlds where that thing exists Mount Everest that's also a proper name and according to kryy it's also a rigid designator and that seems right the name Mount Everest in the actual World refers to Mount Everest in this world it also refers to Mount Everest and then in this world it refers to nothing because Mount Everest doesn't exist but definite descriptions these aren't proper names like this is a definite description it starts with the definite article the word the okay it's called a definite description the 2016 NBA Finals MVP this expression it refers to a different person in different possible worlds in the actual World it refers to LeBron James but in this possible World it refers to Steph Curry it designates it refers non rigidly right it's a non-rigid designator it changes who it refers to depending on what world we're talking about depending on who won Finals MVP in that world the same goes for other definite descriptions like the tallest mountain on Earth in the actual world that expression refers to Mount Everest in this possible world that expression refers to Mount Everest but in this possible world that expression refers to aan kagua in the Argentine Andes a different Mountain the one that would have been the tallest if only India hadn't collided with Eurasia and thrust up the Himalayas okay so that's what possible worlds are and that's what rigid and non- rigid designators are a rigid designator is any term that refers rigidly to the same thing in all the possible worlds in which that thing exists and a non- rigid designator which kryy thinks like definite descriptions are are expressions that refer to different things in different possible worlds depending on how things turned out in those possible worlds all of this goes back to livbits by the way livits was the one who started talking about possible worlds or one of the first or whatever made them famous okay we're done hi it's me in my office if you have a long enough attention span to make it this far in the video then 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Channel: Jeffrey Kaplan

Views: 35,145

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Id: ry84r_gw8HA

Length: 8min 44sec (524 seconds)

Published: Thu Feb 29 2024