 What is it to understand a natural language word? On a popular picture, understanding a word requires that you mentally represent the word’s denotation. For example, understanding the word “cat” requires representing that it denotes cats. LOT theorists will say that you use Mentalese words to represent denotations. The question now arises what it is to understand a Mentalese word. If understanding the Mentalese word requires representing that it has a certain denotation, then we face an infinite regress of meta-languages (Blackburn 1984: 43–44).