This chapter presents Du Châtelet’s account of bodies, in which bodies are causal agents, acting on one another and bringing about change in one another. In developing her account, Du Châtelet introduces a realm of the metaphysically real that consists not of bodies but of non-extended simples or monads. Du Châtelet’s argument against atomism is discussed, along with her recovery of the empirical advantages of atomism despite her commitment to non-extended simples. Her “Argument from Simple Beings to Extended Bodies” is presented. This argument draws on her commitment to determinism and her account of the simples as causally ordered; her account of space and extension; and her views on confused perceptions. The upshot is an interesting idealism about bodies. The relationship of her views to those of Leibniz and Wolff, as well as to the absolute versus relative space and time debate, is briefly discussed. Du Châtelet attributes extension, active force, and passive force to the essence of bodies. Her arguments for attributing active and passive force to bodies are presented, including her rejection of Cartesian occasionalism and her concerns over free will. We see how Du Châtelet developed her account of bodies in accordance with her two-pronged methodology, using the principles of our knowledge (the principles of contradiction and the principle of sufficient reason) and empirical requirements.