According to the Austrian philosopher Hans Kelsen (1881-1973), social and institutional entities are the only entities that can be null, void. The starting point of the article, The “Invalid” and the “Nothing”: At the Origins of Social Ontology, is the analysis of Hans Kelsen’s thesis. But: Why are social entities the only entities that can be null, void? In order to answer this question, in the first part of the article, the author uses two new concepts: validity-imperfection and validity-falsification. The second part of the paper deals with a new ontological question: Are null (void) social entities something?