Why a truly private language is impossible

HostWe all have those moments where we feel like no one else can truly know what's going on inside our heads. You have a specific kind of itch, or a flash of a memory, and it feels like yours and yours alone. It's easy to think we could just give those private feelings our own secret names and keep a little world of words just for ourselves.

HostBut some big thinkers say that's actually not possible, and that a language only one person knows isn't a language at all. Why would we need other people just to name what we're feeling?

GuestIt feels like we should be the kings of our own minds, right? But think about what a word actually is. A word is a tool we use to point at things. There's a famous story about a beetle in a box. Imagine a bunch of people, and each one has a small box. Inside the box is something they call a beetle. Now, the catch is that no one can ever look into anyone else's box. You only know what's in your own. You see your beetle, and you hear everyone else talking about their beetle.

GuestAfter a while, you realize it doesn't actually matter what's in the boxes. One person might have a rock in theirs. Another might have an empty box. But as long as they all use the word beetle to talk about the thing in the box, the word works. The actual thing inside doesn't matter for the language to work. The word beetle just means the thing in the box, whatever it is. If you tried to make a word for something that only you could see, and no one else could ever check, the word would've no job to do.

HostI'm not sure I buy that. If I have a sharp pain in my thumb, I know what that is. I don't need you to look at my thumb to know it hurts. If I want to call that pain "zorp," then "zorp" means that sharp pain. Why does it matter if you can see it?

GuestWell, here is where it gets tricky. Let us say you start a diary. Every time you feel that specific zorp pain, you write the letter S in your book. You do this for a week. On Tuesday, you feel a little twinge and you think, oh, that's S again. So you write it down. But how do you know it was really the same feeling? Maybe Tuesday's pain was a bit duller, or more of a throb.

GuestIn the real world, if you call a dog a cat, I can tell you that you made a mistake. There's a rule outside of your head that we both agree on. But in your private diary, there's no way to check. You're the judge and the jury. If you think it's S, then it's S. But if whatever seems right to you is going to be right, then the word right doesn't mean anything anymore. It's like a man who buys a bunch of copies of the morning paper to see if what the first copy said was true. You're just checking your memory with your memory.

HostBut my memory is pretty good. I know what a toothache feels like. I don't need a witness to tell me I'm remembering my own pain correctly. Why is memory not enough of a floor to stand on?

GuestBecause memory can trick us, and we need a way to find the trick. Think about a clock. If you have a clock on your wall, and you want to know if it's telling the right time, you look at another clock or check the sun. You need something outside the clock itself. If you just look at the clock and say, yes, the clock says it's noon, so it must be noon, you're not really checking anything.

GuestA private language is like a clock that's not hooked up to anything else. If the hands move, you just have to believe them. But a rule you can't break isn't a rule. If I can call anything S whenever I feel like it, then S doesn't have a set meaning. To have a real language, there has to be a way for you to be wrong. And you can only be wrong if there's a shared world where we both look at the same things and agree on the names.

HostSo you're saying that even when I'm sitting alone in a dark room, talking to myself in my head, I'm still using a tool that I borrowed from everyone else?

GuestYeah, exactly. You're using words like dark and room and talk. You learned those by interacting with your parents and friends. You're playing a game with rules that were built by millions of people over a long time. It's like playing a game of catch with yourself. You can throw the ball and catch it, but the only reason it's a game is because you know the rules of how balls and catching work in the real world.

GuestIf you tried to invent a language that was truly cut off from anything shared, you would just be making noises. You would've no way to even tell yourself what those noises meant from one day to the next. You need the rest of us to keep your own thoughts in line. It's a bit like a map. A map that only shows things that only you can see, and that no one else can ever visit, wouldn't be a map of anything. It would just be ink on paper.

HostIt's a strange thought that I need a crowd of people just to have a clear conversation with myself in the mirror.

GuestIt turns out that our deepest, most private thoughts are actually built out of things we all share, like a house made of bricks that everyone in town helped to bake.

HostThe words we use to think with only have value because we all agreed to use the same bank.