  Heidegger's argument here is (at best) incomplete (for discussion, see Dreyfus 1990, Wheeler 2005). The defender of Cartesianism might concede that present-at-hand entities have determinate properties, but wonder why the fact that an entity has determinate properties is necessarily an indication of presence-at-hand. On this view, having determinate properties is necessary but not sufficient for an entity to be present-at-hand. More specifically, she might wonder why involvements cannot be thought of as determinate features that entities possess just when they are embedded in certain contexts of use. Consider for example the various involvements specified in the academic writing context described earlier. They certainly seem to be determinate, albeit context-relative, properties of the computer. Of course, the massively holistic character of totalities of involvements would make the task of specifying the necessary value-predicates (say, as sets of internal representations) incredibly hard, but it is unclear that it makes that task impossible. So it seems as if Heidegger doesn't really develop his case in sufficient detail. However, Dreyfus (1990) pursues a response that Heidegger might have given, one that draws on the familiar philosophical distinction between knowing-how and knowing-that. It seems that value-predicates constitute a form of knowing-that (i.e., knowing that an entity has a certain context-dependent property) whereas the circumspective knowledge of totalities of involvements (Dasein's skilled practical activity) constitutes a form of knowing-how (i.e., knowing how to use equipment in appropriate ways; see the characterization of readiness-to-hand given earlier). Given the plausible (although not universally held) assumption that knowing-how cannot be reduced to knowledge-that, this would explain why value-predicates are simply the wrong sort of structures to capture the phenomenon of world-embeddedness.