Box.

In the 1940s, the philosopher Ludwig Wittgenstein imagined people who each have a box with something in it they call a “beetle.” Nobody can look into anyone else’s box, so everyone knows what a beetle is only from their own.

Wittgenstein pointed out that everyone could have something different in their box. A box might even be empty. The word “beetle” would still work perfectly, because what’s inside never takes part in the conversation.

He was really thinking about words like “pain.” He suggested their meaning comes from how we use them together, not from a private thing inside each of us. His book Philosophical Investigations was published in 1953, two years after he died.

Philosophers still argue about what he meant. If the inside never shows, what exactly are we sharing when we talk about how we feel?