Scientific knowledge as opposed to common-sense knowledge entails a methodological revolution based on a search not for essences, in Aristotelian sense, but for mathematical functions, in Galilean sense, originated from the controlled experiment and founded on the concept of a closed or isolated system. The Priestley-Lavoisier dispute is an historical example that shows clearly the disjunction between pre-science and science. This methodological revolution has not yet been achieved in the field of "social sciences" for the persisting prejudices about dualism between man and nature. Starting from this situation, the paper emphasizes the need for a definition of the research about man and society that overcomes the obstacles and the presuppositions of philosophical ideology and common sense, according to the distinctive features of scientific inquiry and the corresponding requirements for the scientific language. In particular, with reference to the language of every science, the condition of semantic homogeneity of predicates is analyzed, and the main misunderstandings deriving from the non-conformity to this basic criterion (that have so far not allowed a development of a real social science) are pointed out; namely: (a) the consideration of the languages that designate the different fields of research (economics, psychology and sociology) as pairwise disjoint sets, even if there are clear intersections among them, and (b) the resort within the current "social sciences" language to pseudo-functions, whose domain is a set of internal (cognitive) events, or a set of biological events, and the range is a set of external (behavioral) events. According to these remarks, some criticisms to McIntyre's paper, published in this issue, are formulated.