The present study builds on earlier work by Meyer and Land (2003) which introduced the generative notion of "threshold concepts" within (and across) disciplines, in the sense of transforming the internal view of subject matter or part thereof. In this earlier work such concepts were further linked to forms of knowledge that are "troublesome", after the work of Perkins (1999). It was argued that these twinned sets of ideas may define critical moments of irreversible conceptual transformation in the educational experiences of learners, and their teachers. The present study aims (a) to examine the extent to which such phenomena can be located within personal understandings of discipline-specific epistemological discourses, (b) to develop more extensively notions of "liminality" within learning that were raised in the first paper, and (c) to propose a conceptual framework within which teachers may advance their own reflective practice.