In his Philosophical Investigations, Wittgenstein uses an analogy in an attempt to clarify some of the problems involved in thinking of the mind as something over and above behaviour. Imagine, he says, that everyone has a small box in which they keep a beetle. However, no one is allowed to look in anyone else’s box, only in their own. Over time, people talk about what is in their boxes and the word “beetle” comes to stand for what is in everyone’s box.

Through this curious analogy, Wittgenstein is trying to point out that the beetle is very much like like an individual’s mind. No one can know exactly what it is like to be another person or experience things from another’s perspective (look in someone else’s box), but it is generally assumed that the mental workings of other people’s mind are very similar to our own (everyone has a beetle which is more or less similar to everyone else’s). However, it does not really matter – he argues – what is in the box, or whether everyone has a beetle, since there is no way of checking or comparing. In a sense, the word “beetle” – if it is to have any sense or meaning – simply means “what is in the box”. From this point of view, the mind is simply “what is in the box” – or rather “what is in your head”.

Wittgenstein aruges that although we cannot know what it is like to be someone else, to say there must be special mental entity called a mind that makes our experiences private is wrong. Part of the reason he thinks this way is because he considers language to have meaning through public usage. In other words, when we talk of having a mind (or a beetle), we are using a term that we have learnt through conversation and public discourse. Furthermore, the word we have learnt can only ever mean “whatever is in your box” – i.e. your mind – and should not therefore be used to refer to some entity or special mental substance since no one can know that such a thing exists (we cannot see into other people’s boxes).