Abstract“Implicit knowledge” and “tacit knowledge” in Knowledge Management (KM) are important, often synonymous, terms. In KM they often refer to private or personal knowledge that needs to be made public. The original reference of “tacit knowledge” is to the work of the late scientist and philosopher, Michael Polanyi (Polanyi, 1969), but there is substantial evidence that the KM discourse has poorly understood Polanyi's term. Two theoretical problems in Knowledge Management's notion of “implicit knowledge,” which undermine empirical work in this area, are examined. The first problem involves understanding the term “knowledge” according to a folk‐psychology of mental representation to model expression. The second is epistemological and social: understanding Polanyi's term, tacit knowing as a psychological concept instead of as an epistemological problem, in general, and one of social epistemology and of the epistemology of the sciences, in particular. Further, exploring Polanyi's notion of tacit knowing in more detail yields important insights into the role of knowledge in science, including empirical work in information science. This article has two parts: first, there is a discussion of the folk‐psychology model of representation and the need to replace this with a more expressionist model. In the second part, Polanyi's concept of tacit knowledge in relation to the role of analogical thought in expertise is examined. The works of philosophers, particularly Harré and Wittgenstein, are brought to bear on these problems. Conceptual methods play several roles in information science that cannot satisfactorily be performed empirically at all or alone. Among these roles, such methods may examine historical issues, they may critically engage foundational assumptions, and they may deploy new concepts. In this article the last two roles are examined.