This chapter focuses on the role of the teacher in teaching proof and proving in the mathematics classroom. Within an over-arching theme of diversity (of countries, curricula, student age-levels, teachers' knowledge, and so forth), we review three carefully-selected relevant theories: socio-mathematical norms, teaching with variation, and instructional exchanges. Each of these theories starts from the abstraction of observations in existing school mathematics classrooms and uses those observations to probe into the rationality of teachers in order to understand what sustains those classroom contexts and also how such contexts might be changed. We argue that each theory offers insight into the role of the teacher in the teaching and learning of proof and proving. In informing future research, this chapter provides support for meeting the challenge of theorising about the role of the teacher in the teaching and learning of proof and proving in mathematics classrooms across the diverse contexts worldwide
