The understanding that research methodology comprises an essential part of scientific theories about phenomena that are studied is not always brought into the center of theoretical reasoning. The inevitable connection of methodology and statements about the nature of the phenomenon studied becomes obvious when we ask for the proofs of theoretical statements about the phenomenon that a theory should explain. The only scientific way to give the proofs for a theory requires description of the research methodology—who was studied with what assessment methods and which was the exact procedure of data collection. If the analysis of the research methodology reveals questionable procedures or implicit restrictive theoretically not justified assumptions, all theory based on such a methodology must be questioned as well.