A thorny issue

How do we know what pain means? Well, we experience an unpleasant feeling when we are pricked by a thorn, so it presumably refers to those kinds of feelings. While that seems right, "pain" is not just a word that we use to refer to ourselves, we also apply it to others. But how do we know that others feel pain? We don't feel what others feel, so we must infer it from their behavior (e.g., when they groan or say "ouch" or report that they are in pain).

But why would we associate a feeling that we have with the behavior that others have? The reason is that we also observe our own behavior when we experience that feeling. We notice that our behavior, when pricked by a thorn, is the same as other people's behavior when they are pricked by a thorn. Thus, from a young age, we learn that "pain" is the word that we use to talk about those situations.

Of course we nonetheless also experience an unpleasant sensation associated with our own pain behavior. We understand that that sensation is causing our behavior, and the specific sensation we have when pricked by a thorn is what we mean by pain in that circumstance. However it is the publicly observable pain behavior that leads to the word "pain" appearing and being used in our everyday language.

The curious thing about this is that it doesn't actually matter what the feeling is. If others have a different feeling when they exhibit pain behavior or even have no feeling at all (assuming they still exhibit the same behavior, albeit like a robot or a philosophical zombie), the meaning and use of the word "pain" in our language would be exactly the same. Ludwig Wittgenstein discusses this with his beetle-in-a-box analogy and concludes with, "That is to say: if we construe the grammar of the expression of sensation on the model of 'object and designation' the object drops out of consideration as irrelevant." [1]

Later Wittgenstein says (in response to his interlocutor), "'Are you not really a behaviorist in disguise? Aren't you at bottom really saying that everything except human behavior is a fiction?' — If I do speak of a fiction, then it is of a grammatical fiction." [2]

What Wittgenstein is saying is that even though the sensation of pain (and other sensations) is real, our language does not, and cannot, depend on the subjective and private nature of those sensations. Rather our language depends solely on the publicly observable behavior that those sensations produce.

The concept of pain, then, is a publicly communicable abstraction whereas our painful sensations are particular instances of pain. The only way to meaningfully talk with other people about our sensations, to the extent that we can, is via an agreed language grounded in publicly observable phenomena.

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[1] Philosophical Investigations, §293.
[2] Philosophical Investigations, §307.