The First Metaphysical Principles of Natural Science is one of the major works of critical philosophy and undoubtedly the most important work of Kantian philosophy of nature (and an essential part of the Metaphysics of nature, which was never published as a separate work). This treatise is the first systematic attempt at metaphysical grounding of natural science. It deals with natural science as "applied Metaphysics," establishing Physics as a rational science. The First Metaphysical Principles thus constitute the interface between general Metaphysics (i.e., the transcendent part of the Metaphysics of nature that was exposed in the Critique of Pure Reason) and natural science. The theory of the relativity of motion, the critique of atomism, the hypothesis of the continuity of matter, the theory of primary attractive and repulsive forces, the concepts of primary matter and absolute space, the rejection of absolute void and absolute density, all form the conceptual framework of this particular "Metaphysics of bodily nature."