 What matters here is not who is right in this dispute, nor whether Spinoza's Cartesian view is in fact coherent, but Spinoza's strategy. For it is hardly an evenhanded assessment of the experimental results. Spinoza shows considerable ingenuity in interpreting the results of Boyle's own experiments to be consistent with the Cartesian view, and his own as (nearly, anyway) proof positive of it. But he shows no inclination to pursue the question whether his own experimental results can be interpreted along the lines of Boyle's hypothesis, which they can be, easily enough, as Boyle's response (letter 11) shows. Indeed, Boyle complains overall that Spinoza's interpretations of the experimental results are wholly driven by Cartesian theory, rather than a fair attempt to adjudicate between the two alternatives. For example, far from proving the need for the ”very fine matter“ of Cartesian physics, this conclusion has been ”assumed“, by Spinoza, ”simply from the hypothesis of the impossibility of a vacuum“. In other aspects of his interpretation, claims Boyle, Spinoza ‘presupposes Descartes' theory of fire”. Now Boyle's readings of the experimental data are hardly less theory driven than are Spinoza's. But where they differ strategically is in the fact that since the Cartesian theory that drives Spinoza's interpretations is derived by the method of pure rational reflection on perceptions that are a priori clear and distinct, Spinoza clearly grants it a privileged standing in the court of experimentation. On his view, to prove a conclusion that is at odds with one dictated by reason itself, like Descartes', one has to establish impossibility experimentally—which cannot, of course, be done. So long as it is possible to interpret results as consistent with a theory determined by rational reflection alone, those results cannot weigh at all against the theory. Yet experimental results that conform to rationally determined theory confirm it.