a fit of enthusiastic madness
Although one of the definitions in Johnson's Dictionary describes the substantive of this word as "any violent affection of mind or body," in general the connotation emphasized is the temporary state of the affliction. In contrast, Victor's enthusiastic obsession was years in its gestation, and it was succeeded by another, more lethal obsession with the destruction of the being he created. In other words, though the madness he admits to may have taken several forms, it has been unremitting since he entered upon his studies at the University of Ingolstadt. As Victor's diction appears to mitigate its force, it suggests that even now, in his final assessment, he is unwilling fully to engage his own culpability.