This study explores the knowledge-seeking processes among professionals, highlighting three core questions: What induces professionals to engage in continuous learning? What makes them strive for something beyond the immediate obvious goal or situation? How can we theorise practice in a way that allows for engagement and engrossment--the emotional basis of expert work? We attempt to answer these questions by way of a two-step procedure. First, we elaborate the work of Karin Knorr Cetina on the dynamics of desire in expert work supplemented by insights from the work of Gilles Deleuze. Then we use the ideas and visions of these two theoreticians as a sensitising device to analyse the results from an ongoing research project: "Professional learning in a changing society" (ProLearn). The project studies the knowledge-seeking practices of four targeted professions: nurses, accountants, teachers and computer engineers. Although the findings identify practices reminiscent of those of other expert groups, they also suggest areas in which our groups are particularly vulnerable. Specifically, these areas relate to processes of accessing knowledge and developing the sense of mastery which Knorr Cetina and Deleuze point out as essential to the development of a more life-affirmative motive. (Contains 1 note.)