We propose that what teachers can say or write about their views of mathematics and about a range of pedagogic strategies and didactic tactics that they use is of minor importance compared to what comes to mind moment by moment when they are planning or leading a lesson. Beginning with a quote from a teacher that provoked a focus on the role and nature of in-the-moment choices made in the midst of teaching, we offer some comments provoked in us. Following a concise history of attempts to articulate "mathematics needed for teaching", three further brief accounts of incidents led us to propose that what really matters, in the words of Heidegger and others, is one's "mathematical being", because it orients awareness and is the source and basis for choices, whether consciously or unconsciously made. The development of mathematical being is described using the discourse of awareness in the sense of Gattegno, making use of the discipline of noticing to educate awareness. These are then used to extend the analysis of prepositional suffixes for the gerund "knowing" begun by Ryle in order to focus on the development of "connective tissue" between mathematical awareness and in-the-moment pedagogical choices of actions. (Contains 2 notes.)