Mitchell Green argues roughly that one expresses a mental state insofar as one signals and shows it. He writes,
Where A is an agent and B a cognitive, affective, or experiential state of a sort to which A can have introspective access, A expresses her B if and only if A is in state B, and some action or behavior of A’s both shows and signals her B. (212)
First, a signal is a cue that is designed to convey information. There are three types of showing; showing-that, showing-α, and showing-how. Suppose you are sad. You can show-that you are said by providing evidence that you are (e.g. leaving a note saying, "I am sad."). You can show-α you are sad by making it perceptible (e.g. tears). Finally, you can show-how you are sad by displaying your sadness such that one can empathetically know you are sad.
Question: What then is the difference between showing one your sadness and saying that you are sad? Or is it rather that some kinds of showing are sayings, and some are not?