Since the latter half of the 20th century many political efforts and initiatives have been launched to ensure that teacher education provides teachers with a positive (orderly) knowledge base. This includes things like professional teacher standards and notions like 'best practices' and 'evidence-based practice'. Building on the work of Esposito and with inspiration from psychoanalytic theory, we argue that today's educational policy can be seen as an attempt to immunise (teacher) education from risks associated with negativity - disorderly, disruptive and 'destructive' matters that can problematise and question the normal order of things within political debates and policy-based reforms. Drawing on examples from England and Denmark -- contexts in which the authors work -- we demonstrate how a dichotomy between desirable sound/healthy knowledge and undesirable unsound/unhealthy knowledge exist within teacher education. We examine how this produces epistemic injustice in that negative modes of thought and practice are rendered invisible, unthinkable and illegitimate. Being able to traverse such injustice, teachers must be encouraged to approach any and all sources of influence on their professional knowledge base with a sort of agonistic pragmatism, which may allow them to be faithful to the ethico-political situation they are engaged in. What we suggest in this regard is that teacher education must provide time and space for (student) teachers to engage with plurality, contingency and absence because such negative 'stumbling blocks' (always) play a vital part in education, preventing control, stability and harmony.