Realism refers to a relationship between objects and subjects. In the framework of Realism, objects, by necessity are non-contingent, intrinsically discrete, extended entities that, in principle, exist independently of subjects. The fundamental ontology of objects constitutes objective reality. Objects, since they are extended, are any entity that, in principle, can be measured by subjects. Therefore, objective reality refers to the sum of all extended ontological substrate, including energy itself and all of its relations and permutations (particles, space, and time). Importantly, this reality is a species of reality and itself is insufficient to constitute the entirety of reality itself. This reality of the extended ontological substrate simply necessitates that there is being outside of subjects. However, this does not resolve the still more fundamental question of the ultimate source, cause, and mechanism of extension itself. How does extension come to be? In other words, what must necessarily exist for extension itself to manifest?
When we think of things as extended we mean them to have a definite presence in the world and at the same time intrinsic properties that make them existentially unique. We can understand these objects as impenetrable. These objects then, are there to be encountered and measured by other objects. This intersection of objects creates subjects in that each object measures against the properties of the other.