had taken an irresistable hold of my imagination
Once again, Victor yields his will to his passion. But the terms he uses seem to invoke something beyond the question of free will and determinism. Victor at this point recognizes that his imagination, the creative power of fantasy, is driving his pursuit of the unknown, which tends to implicate a faculty ordinarily privileged in British Romanticism. Something of the same order happened four paragraphs earlier, when the imagination was likewise cited (I:3:7).