 Kant was perturbed by Hume’s criticisms of causal relations in nature, implying that there were no laws of nature for science to rely on, and by the antitheological application Hume made of his causal skepticism in the Dialogues Concerning Natural Religion. [See the entry on  Kant and Hume on causality.]  He sought a third way between the Leibnizian “dogmatic” assumption that the universe is a single mechanical system of deterministically interacting physical parts, designed and set going by God, and the empiricist assumption that causality corresponds to a human feeling of anticipation with respect to some sequence of ideas. For scientific purposes, Kant thought, we must represent inorganic nature to ourselves as just such a unified mechanical system. The resolve to represent it as such is facilitated (or perhaps dictated?) by our inability to experience a world unstructured by spatial, temporal, and causal relations. If Leibniz erred by ascribing to unknown noumena the properties of causal closure belonging to phenomena, Hume erred by being unaware of the inbuilt constraints on our representational capacity. But must we represent only inorganic nature — stones, stars, nebulae, planets, billiard balls — as a set of mechanically interacting mechanical systems, or earth’s plants and animals as well? Leibniz was fully committed to the Cartesian claim that plants and animals are machines, no different in principle from automata built from wood and metal parts; though, impressed by the detail revealed by the early microscope, he described them as infinitely complex machines, “machines in their smallest parts, into infinity” (G 6: 618), another indication of the divine origins of nature. Generation and growth were on his view, mechanical processes, for, according to the doctrine of preformation, which he shared with Malebranche, generation is just growth.