This is an article about the struggle for control of knowledge in a divided society. It starts off by describing Belgium as a consociational democracy — that is, a society organized around integrated pillars of society (Catholic, secular), each of which provides a wide range of services (educational, training, health, health insurance, social care, family planning, leisure) to ‘its' people. This special politico-institutional arrangement inherited from the past, though it has evolved, still has profound implications for the way knowledge circulates (or not) and for the way it is used (or not) and perceived both within pillars and across the policy realm: the co-existence of distinct communities requires a form of discretion. The article then goes on to describe the specific incidents that occurred in the course of a recent research project: the authors' written reports produced unexpected effects. They try to make sense of these events by reflecting on how the specific Belgian context can affect and be affected by the production of knowledge about itself. Finally, they extend their reflection to other contexts by emphasizing the general process behind their observation: the transformative effect of knowledge. Knowledge needs to be understood as an act (of construction) that can affect its very object of analysis.