In an anxious world increasingly perceived in terms of risk management, strategies for mapping, articulating and organizing knowledge provide a bulwark against uncertainty. For teacher education, one consequence has been a drive for fullness in relation to knowledge about what teachers should know and be able to do, usually conceived in instrumental terms. Indeed, teacher education, like education more broadly, has been captured by a ‘discursive duopoly’ of instrumentalism, involving the pervasive view that the main purpose of education is to serve the needs of the economy, and consensualism, involving the valorization of agreement regarding this purpose. One way to understand this dynamic in teacher education is in terms of positivity and negativity, whereby the positive refers to social structures, institutions and policies – best practice or teaching standards – that have become reified, while the negative is that which unsettles and disrupts the comfortable stance of the given order of things. Negativity, as a political practice that engages with the positive to reveal the historical and contingent nature of all knowledge, thus offers new conceptual resources, such as antagonism, dissensus, fantasy and impotentiality, for imagining alternative scenarios for teacher education beyond the confines of current policies.