In this paper I address the challenge of developing theory in relation to the practices of mathematics teaching and its development. I do this by exploring a notion of "teaching as learning in practice" through overt use of "inquiry" in mathematics learning, mathematics teaching and the development of practices of teaching in communities involving teachers and educators. The roles and goals of mathematics teachers and educators in such communities are both distinct and deeply intertwined. I see an aim of inquiry in teaching to be the "critical alignment" (Wenger, 1998) of teaching within the communities in which teaching takes place. Inquiry "as a tool" and inquiry "as a way of being" are important concepts in reflexive developmental processes in which inquiry practice leads to better understandings and development of theory.