The development and maintenance of organized cooperative work practices require, as an integral feature, what can loosely be termed ‘didactic practices’ or ‘mutual learning’ (giving and receiving instruction, advice, direction, guidance, recommendation, etc.). However, such didactic practices have not been investigated systematically in CSCW. Michael Polanyi’s notion of ‘tacit knowledge’ vs. ‘explicit knowledge’, which plays a key role in the area of Knowledge Management, would seem to offer an obvious framework for investigating didactic practices in CSCW. But as argued in this article, the notion of ‘tacit knowledge’ is a conceptual muddle that mystifies the very concept of practical knowledge. The article examines the historical context in which the notion of ‘tacit knowledge’ was devised, the purpose for which it was formulated, its original articulation, and the perplexing ways in which it has been appropriated in Knowledge Management. In an attempt to gain firm ground for our research, the article towards the end offers a general analysis of the concept of ‘knowledge’, informed by the work of Gilbert Ryle and Alan White. Overall, the article argues that a framework based on the notion of ‘tacit knowledge’, or on similar conceptions devoted to categorizations of kinds of knowledge, impairs the for CSCW essential focus on actual work practices: instead of focusing on forms of symbolism, what is required is to focus on uncovering the logics of actual didactic practices in cooperative work.