Etiologic research: needed revisions of concepts and principles.

Even though etiologic research has been the central concern in academic epidemiology, its concepts have remained confused or malformed, starting from that of etiology itself; and the same applies to its principles, starting from the notion that the principal variants of an etiologic study are the 'cohort' study and the 'case-control' study. This article suggests revisions of some central concepts pertaining to the object (and objective) of an etiologic study, and it posits an updated conception of the essence--singular--the study itself. This is supplemented by some novel, yet merely orientational, propositions in respect to quality-assurance in etiologic research.