ABSTRACT. Wittgenstein employed a method of "grammatical analysis" to investigate how expressions such as 'to know.' 'to understand,' 'to feel' are actually used and understood. His analysis in the Philosophical Investigations of a conversation concerning the generation of a number series is one of Wittgenstein's most elaborate. In it, he walks us through a process of re-thinking understanding. Throughout, Wittgenstein employs a praxeological approach. It is praxeological, not just because he requires us to look to practices of language use, but also because he guides us in seeing through a practice of modeled reasoning. There is more work to be done, however, before we will be in a position to really understand understanding-in-use.