In 1889 he earned his habilitation in Scandinavian philology with an edition and translation of "The So-Called Second Grammatical Tractate of the Snorra Edda".

[2] In November 1933 he was a signatory to the statement of college and university faculty in support of Hitler and the Nazi regime.

[6] Mogk focussed on the Old Norse texts as literature,[9] and in a number of publications argued that Snorri Sturluson was a mythographer, who composed stories of the Germanic gods to explain poetic allusions rather than reporting pre-existing myths.

[10] For example, he argued that in the passage in the Eddic poem "Völuspá" usually taken as referring to the Æsir–Vanir War, the Vanir were initially within the stronghold with the Æsir and that after the wall was breached, they fought against not the Æsir but the gods' common enemy, the giants; he interpreted Gullveig as a giantess, not one of the Vanir.

Georges Dumézil argued forcefully against Mogk's viewpoint, accusing him of character assassination and a "war" and "sterilisation" of the traditional sources in the field.