The view that the link between words and the world, whereby words mean what they do, is a causal link. The theory is aired in Kripke’s Naming and Necessity for the special case of proper names. A plausible way of thinking of the link between the name ‘Plato’ and the philosopher Plato is that there was an original naming of the philosopher with a term, which is itself an ancestor of the word we use, and a reference-preserving linkage causally responsible for our present use of the term. Even in this case there are difficulties over what makes for a reference-preserving link, and extending the theory to other kinds of term, such as those designating natural kinds, is not straightforward.