Wolff has attached every entity with an essence, which, as it were, contains the kernel of a thing or its central characteristics, from which all features of the thing, or at least their possibility, can be explained. Every thing, whether just possible or actual, has also an essence, or else it wouldn't be a thing. Thus, even world must have such an essence or nature, and the nature of the world (or simply nature) means for Wolff the sum of all principles of mutation inherent in the world, that is, the sum of all active forces in the world.
Now, by natural Wolff simply means something belonging to the nature of any topic. In case of world, natural then means something being or happening in accordance with the forces and laws governing motion. Events that do not happen according to these forces and laws are then supernatural events or miracles. Furthermore, there is an intricate relation between the miracles and laws of motion. Wolff admits that laws of motion are not necessary and that events we would call miraculous are completely possible events of another world. Yet, Wolff goes even further and suggests that miracles can in a sense happen even during the normal course of events – this doesn't imply contradiction, Wolff says, but only the incompleteness of the world we live in. If world is a clockwork, miracle is like a finger entering the works and doing something clock itself wouldn't be able to do. Miracle changes the world, and to do that, it must have adjusted the inner workings of the elements of the world, because elements can exist only in a single world. In order that the world would remain the same world, another miracle will have to follow that changes everything back to how it was.
Laws of motion then define the nature of the world, but they also contribute to its perfection. Perfection in general Wolff defined in his ontology as arising from the unification of a multiplicity under some rules. In case of world, this unification must take the form of a spatio-temporal whole, and the rules governing it are clearly the laws of motion. Thus, when we become aware of the laws governing physical world or the order of nature, we are not just becoming more informed, but also able to appreciate the perfection of the world. Due to the incompleteness of human cognitive capacities, Wolff thinks we can never know the perfection of the world completely – a clever way for Wolff to avoid the possible objection that world does not appear perfect.
Before I completely move away from Wolff's cosmology, I would like to point out how misleading is the Kantian account of what cosmology is about when it comes to Wolff. As it is well known, Kant uses especially his idea of antinomies to undermine the traditional cosmology – reason faces insurmountable dilemmas in its most important questions. Now, ironically the four problems Kant mentions are not treated by Wolff in his cosmology. Problems about human freedom and possible creation of the world are respectively psychological and theological for Wolff, and the questions of the spatiotemporal limits of world and of the divisibility of matter are never comprehensively discussed by Wolff, as far as I can see.
Next time we'll turn to Wolff's empirical psychology.