 This exchange reveals that Elisabeth is committed to a mechanist account of causation—that is, one limited to efficient causation. Elisabeth rejects Descartes’s appeal to the Scholastic conception of heaviness as a model through which to explain mind-body interaction, on the grounds that, as Descartes himself previously argued, it is unintelligible and inconsistent with a mechanist conception of nature. That is, she squarely rejects the formal causal explanatory model underlying the Scholastic notion of a real quality, insofar as she refuses to consider that model appropriate in some contexts. She is nonetheless open-minded about which account of efficient causation ought to be adopted. This openness reveals that she is apprised of debates about the nature of causation in the period (Gabbey 1990, Clatterbaugh 1999, Nadler 1993). Elisabeth’s investment in the new science emerging in the seventeenth century is reflected in what she writes regarding mathematics and natural philosophy, discussed briefly in the next subsection.