We have been studying what Darjes calls primary philosophy, but we finally come to his ontology, when we see his definition of an entity (ens). In effect, by an entity Darjes means something that is not accident, that is, which can be in itself. What this being in itself means, according to Darjes, is at least that in the same place as one entity exists, no other entity can exist. Thus, impenetrability of an entity is an ontological characteristic for Darjes, while accidents might share the same place by occurring in same entity. An entity need not exist, but it can be a merely possible entity. If it does exist, Darjes calls it a substance.
Darjes notes that all substances can contain something which is a reason for something else being what it is. In other words, they are forces that can act on other things. Now, because this activity is an essential part of what substances are, they can also be divided according to their level of activity. The highest kind of substance is completely active and needs at most something to remove obstacles from its way to start acting – they are what Darjes calls an effective conatus. At the lowest rang of substances are completely passive substances, which require some efficient reason to make them act – these are what Darjes calls bare potentia. Between these two extremes fall cases where substances are in some sense passive and in some sense active – these substances Darjes calls either ineffective conatuses or potentias with conatus (it is difficult to say whether Darjes means these two to be separate groups, depending on whether the emphasis is on the active or the passive side of the substance or whether they are just two names for the same thing).
Darjes does not just distinguish between different kinds of forces or substances, but also between different kinds of actions these substances can make occur. The actions might happen within the substances or be intrinsic to it – these would be immanent actions. Then again, the actions might also be extrinsic to the substance – these would be transitive actions. Of course, Darjes also admits that some actions might be partially immanent and partially transitive.
Like all Wolffians, Darjes is a nominalist who insists that no universals can exist. Hence, all substances must be individuals. Although substances cannot then be divided into universals and individuals, Darjes does divide them into complete and incomplete substances, depending on whether a substance acts or not. He also notes that a substance can be variably or contingently complete, if it sometimes happens to act and sometimes not. Even if a substance would be contingently complete, it still might be a necessary existent, since there is no necessity that a necessary existent would always act.
A notion near to completeness is the subsistence of a substance. Darjes defines subsistent substance as a complete substance that is not sustained by something else. Here, sustaining means a relation in which one force determines another to act in a precise manner. Thus, subsisting substance would act and not be acted upon by other substances.
Darjes goes on to define states of an entity. In effect, these are nothing more than collections of some determinations that the entity has. For instance, being a substance or substantiality and subsistence are states that some entity might have. Depending on the determinations making up the state, the state can be internal, external or mixed, and it can be necessary or contingent. For instance, if there are some entities existing absolutely necessarily, then they have an absolutely necessary state of substantiality. With contingent entities, on the other hand, their state of substantiality is also contingent and in fact depends ultimately on some absolutely necessary substance.
Darjes does not remain on mere level of definitions, but tries to determine some general characteristics true of all substances, based mostly on the principle of sufficient reason. The most important conclusion is that all substances must persevere in their state of action or non-action, until some further reason makes them change their state. Thus, an action continues, until something comes to impede it.
Darjes also spends some time considering how to quantify forces. His idea is to measure forces through the actions they can make happen. For instance, if two passive substances have the same quantity of force is they are as quick in producing same actions, then they will produce same action in same time. Thus, by checking what the substances can achieve and how quickly they do it, one can compare the quantity of their forces with one another.