An important feature of world, according to Wolff, is that it is a composite, that is, it consists of parts. Some of these parts are familiar to us from experience. Wolff points out that none of these experienced parts are indivisible, but consist of further parts – we might call them in a modern philosophical vocabulary middle-sized objects.
As composites, Wolff continues, everyday worldly objects must be such that can be completely explained through the structure and mutual relations of these parts – in effect, they are machines similar to the world itself. Because of the dependence, one need just change parts of a middle-sized object in order to change the object itself. In fact, this is the only way to truly have some effect on these objects.
All the changes on the bodies require then moving some stuff from them or moving some stuff in them – that is, movement or motion and direct physical contact is an essential element in changes of the worldly objects. It is then no wonder that a huge part of Wolff's cosmology is dedicated to determining the so-called laws of motion – mostly descriptions of what happens when several bodies collide with one another, depending on their size, mass, velocity and cohesion. Although determining what the correct laws of motion were was an ongoing philosophical and scientific theme at least from the time of Descartes' Principia philosophiae, I won't go into any further details here, besides one exception.
The one interesting element in the laws of motion is the notion that a resting body will not by itself start to move and that a moving body will not by itself change its velocity or direction. This property, known nowadays as inertia, is called by Wolff a passive force of a body, and according to him, should be taken as defining what is called matter, which he takes to be the extension of passive force. With just matter, bodies would then just have stayed in the same place for all eternity. The movement must have then been generated by something else, that is, by an active force, which is then transferred from one body to another in various collisions. Matter and active forces are then what one requires for explaining the constitution of our world and they might be taken as substances in what we observe of the world.
Yet, matter and active forces are not the whole story. As I've mentioned in a previous text, beyond the level of material bodies exists the level of elements of bodies, because as composite entities material bodies must ultimately consist of some simple entities. As simple, these elements cannot have any extension and are therefore indivisible. They are not like atoms are thought to be, Wolff says, because atoms are supposed to have no true distinguishing qualities, which would contradict the ontological principle that no two entities can have exactly same qualities.
The differentiating principle of the elements, Wolff suggests, should be their conatus, that is, the basic force containing in nuce all the changes that will happen to a particular element. In effect, elements are differentiated by their whole life history. Because an essential part of a life history of an element consists of its interactions with other elements and these interactions are essential part of a nexus forming a world, an element cannot exist except in a single world, that is, by changing world you must change also its elements and vice versa.
The actual relation of elements to bodies is rather confusing in Wolffian philosophy. What is clear is that elements constitute the realm of bodies we observe. This means that many features we appear to observe in bodies must be deceptive. For instance, bodies appear to consist of continuous masses of such types of stuff as water. Yet, because all matter and even water must consist of individual, indivisible and completely distinct elements, they must actually be discontinuous. What is unclear is how this phenomenal realm of continuities is supposed to arise from true realm of discontinuities. The question is muddled even more by corpuscles, which Wolff introduces as constituting a level between observed bodies and elements. The behaviour of bodies Wolff explains as constituted by the corpuscles, parts of body, which still are divisible. Yet, no explanation is given how corpuscles are generated from the level of elements, and number of confusing questions remain. For instance, should a corpuscle consist of an infinity of elements?
This enigma is a point where we must leave the Wolffian concept of microcosm. Next time I still have something to say about the order and perfection of the world in Wolff's cosmology.