“…They have found that, as a group, teachers have resources to justify positive appraisals of certain elements of the work of proving: the use of an unproven conjecture as a premise in proving a target conclusion; the identification of new mathematical concepts and their properties from objects introduced and observations made in justifying a construction; the deductive derivation of a conditional statement connecting two concomitant facts about a diagram; the prediction of an empirical fact by operating algebraically with symbols representing the quantities to be measured; the breaking up of a complicated proof problem into smaller problems (lemmas); the application of a specific proving technique (e.g., reduction to a previously proven case); and the establishment of equivalence relationships among a set of concomitantly true statements. Herbst, Miyakawa and Chazan (2010) have proposed that teachers might use the various functions of mathematical proof documented in the literature (e.g., verification, explanation, discovery, communication, systematization, development of an empirical theory, and container of techniques) (de Villiers, 1990;Hanna & Barbeau, 2008;Hanna & Jahnke, 1996) to attach contractual value to actions like those listed above. There remain two questions; whether classroom exchanges are possible (manageable) between these actions and the elements of currency; and whether the exchanges can be contained within instances of the 'doing proofs' situation or otherwise whether they require more explicit negotiations of the didactical contract.…”