This article engages critically with the theory of expression proposed by Mitchell Green in his Self-Expression. In this book, Green argues that expressions are signals designed to convey information about mental states. By putting pressure on one of the examples Green uses in his book, I will challenge this thesis. I will then deepen this challenge by developing a contrast between two philosophical perspectives on expression, which I name the 'instrumental' and the `descriptive'. I take Green's theory of expression to (...) be an exemplar of the instrumental perspective. Expression, in the instrumental perspective, is a means for transmitting information about mental states from organism to organism. The descriptive perspective I articulate with the help of Maurice Merleau-Ponty and Ludwig Wittgenstein. On the descriptive view, expression is an answer to the question what it is so much as to have mental states and a living body. I suggest at the end of the article that if we remain within the instrumental perspective, we will not be able to use expression to satisfactorily answer this question. (shrink)