This article deals with the epistemology and methodology that the ethnographic investigations require, that is to say, those researches that try to describe and to interpret the modalities of life of those persons who live in groups. The ethnographic approach leans on the conviction that the traditions, roles, values and norms of the enivironment in which one lives is internalized little by little and generate regularities that can explain the individual and group behavior in appropriate form. Indeed, the members of an ethnic, cultural or situational group share a logical or reasoning structure that, in general, is not explicit, but that one manifests in different aspects of his life.