In this paper, there is given a historical review of the recent stratigraphical classification that is standing on the dualismic conception as the lithological and chronological divisions are to be separated distinctly from each other., A short discussion is offered on the scientific and social backgrounds of this dualismic conception in the process of its birth and development., This dualismic conception has the intimate relation with the geometric conception or formalism which dominated from the time of Aristoteles, even in the world of sciene., This conception supports unconciously the principle of geometric extension, that is to say the distribution of the material observed in detail on the surface of the earth may suggest the undeerground extension of it., The practical experience, however, denies it., The distribution of materials on the earth, is subjected to the geological movement that concentrates, transports, deposits or decomposes all the materials of the earth., It is clear, then, that the observed distribution of the materials never warrants the underground extension of them, but only the geological movement of the earth, nallow or broad, traced and substituted from the relations among the materials distributed there, can show the underground distribution precisely., This is why the writer and Miss U., Kitazaki proposed lately the geohistorical classification of the strata, synthesizing the lithological and chronological classifications.,