The doppelgänger or double is a feature of gothic tales throughout the eighteenth
and nineteenth century. As a literary type, however, the double can have more than
sensational uses. Within a year of Frankenstein's publication, for instance, Percy
Bysshe Shelley incorporated the figure within the first act of Prometheus Unbound,
where the Earth tells Prometheus of a second realm of potentiality that shadows the
actual world:

     Ere Babylon was dust,
The Magus Zoroaster, my dead child,
Met his own image walking in the garden.
That apparition, sole of men, he saw.
-- I.191-95

Mary Shelley, too, is concerned with potentiality, both its development and its thwarting,
which she pursues on a number of different levels in this novel, projecting the doubling
on moral and psychological, but also on mythic and theological, grounds. Up to this
point in the novel the theme of doubling has been only hinted at in the intensities
of male friendship we have encountered. Here, in directly introducing doubling as
a psychological condition, her basic stress is on the self-division and resulting
self-destructiveness that, we may now begin to realize, is the driving force behind
the arctic pursuit that initiates Victor's narrative.

Mary Shelley quotes from Byron's Childe Harold's Pilgrimage, Canto III, stanza 62,
written the same summer, 1816, in which she began Frankenstein.

. . . Above me are the Alps,
The palaces of Nature, whose vast walls,
Have pinnacled in clouds their snowy scalps,
And throned Eternity in icy halls
Of cold sublimity, where forms and falls
The avalanche—the thunderbolt of snow!
All that expands the spirit, yet appals,
Gather around these summits, as to show
How Earth may pierce to Heaven, yet leave vain man below.
-- III.590-98

Health in this novel is something of a moral index. Victor's physical collapse results
from his obsessiveness and introversion. His father, who loads him with moral maxims
(I:3:10 ), in contrast, renews his vigor as Victor's is sapped.

Joseph Priestley, 1733-1804, a founder of modern chemistry particularly noted for
his discovery of oxygen, was a friend of Mary Shelley's father Godwin in the 1790s.

An interesting phrase, suggesting Victor Frankenstein's mature awareness of his own
limitations as well as Mary Shelley's compassionate sense of human fallibility, a
characteristic that, since it is commonly shared, might well serve as a universal
restraint upon human overreaching.

Walton refers to previous explorers of the northern wilderness. Sir John Ross, in
the Introduction to his Narrative of a Second Voyage in Search of a north-west passage
and of a residence in the Arctic Regions during the years 1829, 1830, 1831, 1832,
and 1833 (London: Webster, 1835), pp. i-xxiv provides a useful, near-contemporary
history of such expeditions.