There’s a somewhat famous, or rather infamous, passage from Ludwig Wittgenstein, a philosopher from the mid 20th century, where he talks about a beetle in a box. Let’s now read his infamous thought experiment and try to make sense of it.
Suppose everyone had a box with something in it: we call it a ‘beetle’. No one can look into anyone else’s box, and everyone says he knows what a beetle is only by looking at his beetle.—Here it would be quite possible for everyone to have something different in his box. One might even imagine such a thing constantly changing.—But suppose the word ‘beetle’ had a use in these people’s language?—If so it would not be used as the name of a thing. The thing in the box has no place in the language game at all; not even as a something: for the box might even be empty.— No, one can ‘divide through’ by the thing in the box; it cancels out, whatever it is. (1958, §293)
One of the possible interpretations of this passage is that it shows that mental experiences such as pain are not merely private phenomena, i.e., that pain is only accessible to the one experiencing it and that introspection is the only way you can know what pain is.
But before we move on to mental phenomena, let’s focus on Wittgenstein’s example of the word ‘beetle’. The idea is that this word cannot be used successfully in a conversation if we can only know the meaning of the term privately, that is, if we know the meaning merely by ourselves, in isolation. In other words, it would be impossible to communicate if the only way to know the meaning of ‘beetle’ is by looking into our own private box. It would be impossible because our boxes may contain entirely different things. The only things that we can successfully talk about are public and, since we can successfully talk about beetles, we must accept that the term refers to something that is public. Moreover, if we want to know what a beetle is, we have to look at the ways in which the speakers use the term ‘beetle’ and the same applies to any other thing.
By analogy, we can also argue that mental experiences are not merely private. If the word ‘pain’ is meaningful, we cannot know its meaning by just looking into our private “pain box”. If pain was completely private, then the pain in your box and the pain in my box could be completely different, they could be changing all the time, and our boxes might even be empty. If your pain was completely different from mine, it could be that, in fact, your pain felt like my tickles and vice versa. In this way, one might think, if pain was completely private and we could only know it through introspection, then it would actually be impossible to have a conversation about pain. It would be impossible because we could be talking about completely different things!
Instead of thinking that pain is private, one could argue that we do have meaningful conversations about pain, which shows that pain must be public. For example, when we go to the doctor, we have a meaningful exchange about our pain and how to cure it. When I tell you that I have a bad migraine it seems that you know what I mean. If we accept that we have meaningful communication about pain, this means that pain is not a merely a private experience: mental experiences, such as pain, must be public phenomena.
Even if the passage from Wittgenstein is controversial, it provides an interesting insight about the nature of the meaning of words and the nature of mental experiences. Further, contrary to people’s first intuition, this passage offers the basis for arguing that something that seems completely private, such as one’s mental experience, actually has to be a public phenomenon —if we can successfully talk to each other about it.
Here’s a short video explaining the passage:
Wittgenstein, L., (1953), Philosophical investigations, translated [from the German] by G. E. M. Anscombe, Oxford : Blackwell, 1968.