The (superior) competitive position of the firm's products (or services) in its markets is thought to be the expression of the firm's competitive advantage. Hamel and Prahald go on to assert that core competencies are the result of "collective learning across the corporation". Since that publication there has been active debate in the academic literature as to whether (the concept of) "core competencies" is the same notion as core capabilities. Several authors consider that the concepts are the same, the differences purely terminological, and use the terms interchangeably while others insist there is a substantive distinction. Given the similarities in their definitions it is a reasonable position to think they are the same. However, neither Leonard, nor Hamel and Prahalad (nor indeed Kay) were philosophically precise enough in their definitions and expositions of the concepts for the identity to be definitively established. One reasonable position is that "core competencies" are a view of "core capabilities" from a customers and products perspective while "core capabilities" are a view of "core competencies" from the perspective of knowledge and skills and staff and suppliers in firms. This may reflect the philosophical biases of their respective institutions. Others, such as Max Boisot, take the view that competence or competency is some measure of the level of performance in a capability or that competence is a much narrower concept than capability. Hence a firm may have a high or low level of competence in a particular, notional, abstract capability. There is some evidence that general managers often fail to appreciate the subtlety of the definition of "core competencies" and over-estimate the degree of their firm's competence in common capabilities. Consequently, they over-identify "things the firm is good at" as core competencies – which falls foul of the distinctiveness criterion for a core capability (and/or the inimitability criterion of core competencies and core capabilities). Hence some things managers mistakenly identify as "core competencies" may be more properly considered as Enabling or Supplemental Capabilities. When applying the concepts of "core competence" or "core capability" academics and practitioners should be clear and precise as to their intended semantics for these ambiguous terms. Leonard analyzes the nature of a (business) capability and concludes that core capabilities "comprise at least four interdependent dimensions" (pp. 19) as follows:  Around this complex of systems that realize a core capability Leonard situates a loop "Capability-Creating Activities" that comprise "Shared Problem Solving" and encompass Present and Future and Internal and External Perspectives (see Leonard, 1995, chapter 3).