  Precisely because the elements of matter are simple, unextended active monads, what we see around us as extended must be merely phenomenal, and she does endorse this   Leibnizian-Wolffian[13] conclusion. Throughout her seventh chapter “On the Elements of Body”, she follows the Leibnizian tradition in concluding that metaphysical reality must consist in unextended monads. Consequently, what we see in nature as extended must be mere phenomena and not real in the fullest metaphysical sense. She concludes, for example, that phenomena, known best through sense, result from the confusion of simple beings (IP §152–5), and that just as monads are characterized by active and passive force (now termed primitive force), so too are phenomenal bodies to be thought of as possessing force—both derivative active and passive force (IP §158–9). Thus, suppositions such as Newton's that the natural world can be described with reference to inelastic, invisible, extended atoms must be suppositions not about ground floor metaphysics but about the derivative physical world which is merely phenomenal in a broadly Leibnizian sense. This has led Linda Janik to helpfully characterize Du Châtelet's account of the created world as a three-tier account (Janik 1982, 106): the basic metaphysical tier of unextended monads, the subvisible physical tier of (for Du Châtelet) extended matter which is also imbued with derivative force, and the visible physical tier of bodies in motion and at rest. Without working through the details of her picture, including the coherence or difficulties with it, what this three-tier account permits is significant separation between metaphysics and physics. We see this when we consider the following. We can know that there is a systematic interconnection among all elements of the created world—the PSR, together with what we can derive of God's nature seem to establish this for Du Châtelet—we cannot always know all the details of that systematicity. Moreover, we can expect that this systematicity occurs most fundamentally at the level of ground floor metaphysics—that is, among unextended monads. But Du Châtelet does not spell out in detail how exactly the metaphysical tier and physical tiers are related to each other (Iltis 1977, 36–7). And so, while the systematic interconnectedness we experience at the level of phenomena—the realm of physics, that is—surely has some grounding in metaphysics, crucially, we cannot know many details of the connection among realms. While it is certainly true that there is some connection between the metaphysics and physics—for example, the force, which belongs to monads explains the brute phenomena of motion and rest in the physical world—physics does enjoy significant autonomy from metaphysics (Janik 1982, 106; Barber 1967,   209).[14]  We see the impact of this on her physics in §6 below.