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What a private language is

"If someone were to behave as if they understood a language of which no one else can make sense, we might call this an example of a private language.[3] It is not sufficient here, however, for the language to simply be one that has not yet been translated. In order to count as a private language in Wittgenstein's sense, it must be in principle incapable of translation into an ordinary language – if for example it were to describe those inner experiences supposed to be inaccessible to others.[4] The private language being considered is not simply a language in fact understood by one person, but a language that in principle can only be understood by one person. So the last speaker of a dying language would not be speaking a private language, since the language remains in principle learnable. A private language must be unlearnable and untranslatable, and yet it must appear that the speaker is able to make sense of it."

I'm having trouble seeing what "in principle can only be understood by one person" means. Suppose all humans have died except one. He understands English but now he can't write or speak anymore. Let's say all records of English have been destroyed. The last human just relies on his memory of English for his own internal thought process. Would English in this situation count as a private language in Wittgenstein's terms?

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    What actually happens to a language has nothing to do with who can in principle understand it. Since English is already understood by multiple people it is so in principle no matter what happens or can happen. SEP is a much better source on subtleties than Wikipedia:"The words of this language are to refer to what only the speaker can know — to his immediate private sensations", PI.243
    – Conifold
    Commented May 23, 2020 at 9:02
  • So if I create a symbol for "pain in my left hand"... but I don't tell anybody about what the symbol is or what it means... does that constitute a private language? Commented May 23, 2020 at 9:10
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    "Pain" has a public meaning, but if you made a symbol for your private quale it wouldn't matter if you tell because there is nothing you can tell that would convey any meaning to others. Of course, according to Wittgenstein's analysis it turns out, in the end, that it conveys no meaning to you either, so this is a bit like explaining what a round square is before explaining why it really isn't anything.
    – Conifold
    Commented May 23, 2020 at 9:20
  • But what constitutes "private quale". For example... to me it is utterly clear that when I say something is blue I'm referring to a private sensation. I assume this would not be considered a "private quale"... so my question is what would... as an example. Suppose I have hallucinations of a ghost/demon like-thing that nobody else can see. I assign this hallucination an invented word "goroff" without telling anyone else... is that a "private quale"? If so, would Wittgenstein be saying I don't know what "goroff" means... Commented May 23, 2020 at 14:46
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    @Conifold, "You say it because you expect others in the community to accede to it under normal circumstances." What about abnormal circumstances? Suppose I wake up one day with some sort of eye-defect, and the sky looks yellow to me. I say out loud "the sky is yellow today". Everyone else disagrees and says, "The sky is blue as usual.". If private quales are incoherent, then what is the explanation for why I say the sky is yellow? I mean isn't the normal conclusion that I and everyone else will come to: "He is seeing yellow, while we are seeing blue".? Commented May 24, 2020 at 5:21

2 Answers 2


A private language according to Wittgenstein is a language that -- in principle -- can only be understood by one person. Put differently, the meaning of its sentences and words is very principally only accessible by this singleton.

The typical dummy of a private language, Wittgenstein fights, is a language of private sensations.

According to this dummy

  • the meaning of "red" is private because each of us has a different sensation of red
  • a blind could actually not understand what "red" means because she lacks any sensation of red

Now, according to Wittgenstein it's all the other way around. As matter of fact, we do understand each other when talking with words like "red". Even a blind person is quite competent in the use of "red". This proves that private sensations are (almost) irrelevant for the meaning of "red" and that, hence, "red" is public.

Wittgenstein would go even further and argue for the impossibility of private languages. As all language is based on rules and rules are (formulated in) public (language), there cannot be a private language.

As usual, Wittgenstein, the elliptical genius, has a point.

  • So someone who is blind from birth knows what "red" means? If "red" does not mean a sensation of red, what does it mean? Commented May 23, 2020 at 14:36
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    The meaning of "red" constitutes itself through the true and false sentences "red" is part of. A person who can tell true and false of sentences "red" is part of knows something about the meaning of "red". Hence, a blind person may know more about red than a seeing person.
    – user14511
    Commented May 23, 2020 at 14:45
  • Ok. And how is the truth and falsity of the sentences decided upon? Commented May 23, 2020 at 14:54
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    Through the theory these sentences are part of. The theory of physics has a lot to say about colors. A blind physicist must be an expert of red.
    – user14511
    Commented May 23, 2020 at 14:56
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    You're getting closer. :-) To be is to be the value of a bound variable (Quine). Something that cannot occur in language as value of a bound variable cannot exist. And there go, I am afraid, private sensations.
    – user14511
    Commented May 23, 2020 at 15:08

A language, by definition and in practise, is used for communication, whether privately amongst a group, as in argot, or publicly, as in language. Thus Wittgensteins notion of a private language is actually badly named, since in fact it's not langauge at all.

But given that there is no term that described what he was referring to, he co-opted terms and gave them a new meaning. This happens all the time. For example, television means far (tele) seeing (vision). And whilst it is not far seeing with your own eyes, to take the term literally, one can see why the term has been used. Likewise with Wittgensteins notion of a private language.

But philosophically speaking, one should not confuse it with a language per se.

  • When Wittgenstein called it a mlrf gblorbl no one knew what he was talking about. "Use your words!" actually means, use my words.
    – Scott Rowe
    Commented Oct 8, 2023 at 13:18

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