A long-standing debate in the philosophy of the social sciences revolves around the following question: what is the mode of existence of socially grounded phenomena such as corporations, social groups, money and presidents? Philosophers and social scientists have generally assumed that there are two main options: either social phenomena are reducible to lower-level phenomena (to individuals and material objects represented in certain ways) or else they are phenomena of their own kind (sui generis) existing at a higher level. However, recent work in social ontology, partly by the applicant, has revealed that neither of these two options is plausible. Building on theoretical advances made in analytic philosophy concerning so-called ‘truthmaker theory’, the current project cuts the Gordian knot by defending a third option hitherto overlooked in social ontology. In the project it will be shown in detail how a theory of truthmakers for statements about social phenomena can account for the truth of such statements, without the fatal problems afflicting the orthodox theories surfacing. The alternative, innovative explanatory model and its various applications to social ontology will be presented in a unified monograph in English building on articles in international philosophy journals by the applicant.