 Wolff contends that PC is not only for our thinking but, in defining the limits of what is conceivable or not, also serves to distinguish the possible from the impossible. So, impossibility, defined formally, is that which involves a contradiction, whereas that which does not is taken to be possible. Now for Wolff, “possible” and “possible thing” are basically synonymous terms. What is possible as a concept is simply reducible to what is possible as a thing. The realm of concepts and the ontological realm of objects converge in the Wolffian system (Kuehn 1997). A thing or “being” is defined as “that which does not involve a contradiction” (Ont. §135). A possible concept, consequently, is that which corresponds to a possible object (Ont. §§57, 59, 60). This analysis of the concept of the possible typifies Wolff’s non-existential and essence-centered approach to ontology. Very briefly, Wolff’s understanding of being (or what is) involves regarding being in its most general sense. A being is “something” if and only if it is intrinsically possible, and something is intrinsically possible, if and only if its predicates or “determinations” are not contradictory. “Nothing”, in contrast, is simply a term that is empty of all content. In the ontological realm of objects there is literally no thing to which “nothing” corresponds (Ont. §57). Nothing, by definition, is not thinkable or conceivable.