Vico's doctrine of mythology, while no less original and profound than that of poetry, is also, like the latter, not entirely lucid: for the relations between poetry and myth are so close that the shadow cast upon the one must of necessity extend to some degree over the other.
In proceeding to inquire, as we have hitherto done and shall continue to do, into the state of contemporary knowledge of the several sciences and problems with which Vico set out to deal, we may briefly recall _à propos_ of the study of mythology not only the great literary collections of myths formed during the sixteenth and seventeenth centuries, of which Boccaccio had already given an example in the fourteenth century, but also the learned defences of the two explanatory theories, already known to classical antiquity and not entirely unknown in the Middle Ages. These were, first, the theory of myth as allegory of philosophical truths (moral, political and so forth), and secondly, the theory of myth as the history of actual persons and events, adorned by the fancy which made heroes into gods (Euhemerism). The former tendency inspired among other works the _Mythologiae sive explanationis fabularum libri decem_ of Natale Conti (1568) and Bacon's _De sapientia veterum_ (1609); in which, however, this system had been advanced with a certain hesitation, and with the explicit caution that, even if it were not valid as historical interpretation, it would always be of value as moralisation (_aut antiquitatem illustrabimus aut res ipsas:_ "we shall explain either antiquity or the facts themselves"). The latter was authoritatively represented by John Leclerc (Clericus), the learned Dutch Genevese for whom Vico expressed so much respect and gratitude for the attention he had deigned to bestow upon his _Diritto universale._ His edition of Hesiod's _Theogony_ marked an epoch in the study of mythology, and he was followed among others by Banier, author of the work _Les Fables expliquées par l'histoire_(1735). A third system, also not without some ancient precedent, derived myths from particular nations, the Egyptians or the Hebrews, or from the original works of individual philosophers and poets. This view, when it neither resolved itself into a pure and simple historical supposition as to the origin of some or all myths, nor appealed to divine revelation, clearly involved the theory that myth is not an eternal form but a contingent product of the mind, born at a certain time and capable of dying or already dead.