This paper shows, from the ontology and the philosophy of language, a series of characteristics of social sciences that proves the conceptual impossibility to join them with natural sciences as a unique science.Philosophical characteristics of social sciences' subjects (ontology of social reality), such as some features of the language that defines the social reality, illustrate that the structure of conceptual scheme of social sciences is, largely, incommensurable with the structure of natural sciences.So the text tries to explain, especially from the philosophical theses of John Searle, that the ontology of social sciences and the linguistic schemes in which is described and through which becomes the social reality, exhibit features that make about it unapproachable by natural sciences.The final objective around the over-documented methodological distinction between social and natural sciences, is to show reasons from ontology and philosophy of language for arguing the conceptual impossibility, but not methodological, for comparing both kinds of knowledge.