A canon and librarian of the abbey of Sainte-Geneviève in Paris, Le Bossu is the author of a systematic comparison of Aristotelian and Cartesian physics (the latter often being actually Jacques Rohault's version). Surprisingly, Le Bossu believes that they can be reconciled. How can such a feat be achieved? Le Bossu thinks that the difference between Aristotle and Descartes is above all a matter of presentation. Descartes (in the Principles) systematically expounds a full-fledged science, which, Le Bossu (1674, 314) contends, Aristotle possessed but did not want to divulge! Thus, Descartes dismisses the testimony of the senses and starts with the most general principles, such as motion, from which he deduces the properties of particular bodies (Le Bossu 1674, 203–4). On the contrary, Aristotle starts with immediate, sensible experience and regresses by induction to the causes, because his presentation is a propaedeutic, suitable for beginners. Similarly, whereas Descartes sets forth his principles (matter and form only) as the real constitutive principles of things, Aristotle proposes the fundamental concepts of his physics (matter, form, privation) as heuristic principles only. Aristotle does know that there is no real privation in things, Le Bossu contends (1674, 84–89); speaking of privation is only a methodological detour to discover what role the form plays with respect to matter. Thanks to some adjustments, the Cartesian and Aristotelian concepts of form and of matter are then declared to be compatible. Form, for instance, is to be understood as the arrangement of parts of matter that makes a thing what it is. Along the same lines, Le Bossu (1674, 209–11) even claims that the Aristotelian notion of potentiality is to be interpreted as the relative rest between the parts of a same body, and that the actualization of this potentiality consists in the local motion of this body in Descartes’ sense.

Since in unpublished memoirs he apparently supported Descartes’ views on animals and showed sympathy for his explanation of transubstantiation, Le Bossu's interpretation must be seen as a way of making Cartesianism acceptable to traditional minds. However, the result of his endeavor is faithful neither to Aristotle nor to Descartes.