When I started working on the history of linguistics — which had been totally forgotten; nobody knew about it — I discovered all sorts of things. One of the things I came across was Wilhelm von Humboldt’s very interesting work. One part of it that has since become famous is his statement that language “makes infinite use of finite means.” It’s often thought that we have answered that question with Turing computability and generative grammar, but we haven’t. He was talking about infinite use, not the generative capacity. Yes, we can understand the generation of the expressions that we use, but we don’t understand how we use them. Why do we decide to say this and not something else? In our normal interactions, why do we convey the inner workings of our minds to others in a particular way? Nobody understands that. So, the infinite use of language remains a mystery, as it always has. Humboldt’s aphorism is constantly quoted, but the depth of the problem it formulates is not always recognized.