No firm dates can be assigned to this emperor's life or reign. Kōgen is regarded by historians as a "legendary emperor" because of the paucity of information about him, which does not necessarily imply that no such person ever existed. Rather, scholars can only lament that, at this time, there is insufficient material available for further verification and study.
In Kojiki and Nihonshoki only his name and genealogy were recorded. The Japanese have traditionally accepted this sovereign's historical existence, and an Imperial misasagi or tomb for Kōgen is currently maintained; however, no extant contemporary records have been discovered which confirm a view that this historical figure actually reigned. He is considered to have been the seventh of eight emperors without specific legends associated with them, also known as the .
Later generations may have included this name to the list of emperors of Japan, thus making him posthumously an emperor and assigning him as one of the early sovereigns and ancestors of the dynasty that has reigned unbroken since time immemorial. If he lived, at his time the title tenno was not yet used, and the polity he possibly ruled did certainly not contain all or even the most of Japan. In the chronicle which encompasses his alleged successors in beginnings of historical time, it becomes reasonable to conclude that Kōgen, if he existed, might have been a chieftain or a regional king in early Yamato tribal society.
Jien records that Kōgen was the eldest son of Emperor Kōrei, and that he ruled from the palace of Sakaihara-no-miya at Karu in what will come to be known as Yamato province. The Abe clan are said to have descended from a son of Emperor Kōgen.
Kōgen is a posthumous name. It is undisputed that this identification is Chinese in form and Buddhist in implication, which suggests that the name must have been regularized centuries after the lifetime ascribed to Kōgen, possibly during the time in which legends about the origins of the Yamato dynasty were compiled as the chronicles known today as the Kojiki.