When we use words, we tend to assume that others are using them in the same way as we are. If they do not, that will cause a problem for understanding and evaluating each other's reasons, or for any sort of communication. But there is plenty of evidence that we usually don't know exactly what words mean.

We will only consider one simple class of words - nouns. Nouns are words that describe a category of similar things. Nouns include:

Chair, Sheep, Soup, Money, Idea, Country, Philosopher, and Emotion.
Of all these, we might think that 'chair', 'sheep', and 'soup' are the easiest to define. But the meaning of 'chair' has long been discussed by philosophers and furniture-designers alike. Is a chair defined by being primarily for sitting on? Must it have four legs and a back? How does it differ from a small couch? Is 'chair' a cross-cultural constant, or do different cultures have conflicting ideas of what is acceptable in a chair? Similarly, 'sheep' - like all species terms - has been shown to be effectively undefinable by biologists and philosophers of biology. We can't even say when a sheep becomes a goat, because there are too many intermediate cases. Soup.png

So, that leaves us with 'soup'. Surely, we know what we mean by soup, or at least we should recognise soup when we see it. And we would expect a great deal of agreement between people, at least those with a common cultural background. Fortunately, a philosopher (Stefano Gualeni) has decided to investigate our concept of soup, and has devised an interactive thought experiment, or short online game, to help you to decide what your "rules of soup" are.

Stefano summarises his research results as: "Definitions of 'soup' are established by what is most commonly present in (or with) them. We noticed that, when presented with different soup examples, people were more conceptually inclusive than they were in their definitions." And that fits with research about how we use and define most terms. We often make our definitions too narrow, and then allow exceptions or border-line cases when we think of them.