Victor uses a simile and a metaphor and alludes to physicist Sir Isaac Newton when he describes his thirst for knowledge to Robert Walton in Chapter 2:
Sir Isaac Newton is said to have avowed that he felt like a child picking up shells beside the great and unexplored ocean of truth.
Sir Isaac Newton, noted physicist and mathematician of the 17th and 18th centuries, represented the powers of scientific knowledge, in particular man’s pursuit of it. Knowledge—"the ocean of truth” —is metaphorically depicted as limitless and expansive like the open waters of the ocean, and the pursuer of said knowledge is compared to a wandering, innocent child—small and helpless compared to the vast deeps, yet delighting in the beauties and mysteries there for him to discover.
Victor’s seashell simile also draws a connection between nature and progress. Walton, an explorer, sees nature as a source of knowledge. Likewise, Victor attempts to “pioneer a new way” by digging deep into the “citadel of nature.” Nature, for these men, is unknown territory to explore. However, the novel’s tragic events suggest that nature, rather than humankind, actually has the upper hand. Victor’s misguided attempt to master nature only leads to his downfall.
In Chapter 4, Victor uses a metaphor of light to describe his reaction after discovering the secret to life:
Life and death appeared to me ideal bounds, which I should first break through, and pour a torrent of light into our dark world. A new species would bless me as its creator and source; many happy and excellent natures would owe their being to me. No father could claim the gratitude of his child so completely as I should deserve theirs.
Victor’s scientific ambitions have become so extreme that he now sees himself as a God, all-powerful and able to manipulate life and death. Victor, believing he has conquered nature, even envisions going on to create a new version of man. Dreaming of this possibility, Victor imagines pouring a "torrent of light" into the “dark world,” a metaphor that represents the infusion of knowledge into a world characterized by the "darkness" of ignorance. Victor assumes his discoveries will be a gift to human society, and more importantly he is concerned about what they will do for his status among those creatures indebted to him for his role in creating them. Through the events of the novel, Shelley offers a cautionary tale, a moral warning on the dangers of heedless ambition.
In Chapter 8, Victor uses the metaphor of the "never-dying worm" to express his guilt after Justine Moritz, his brother William’s nanny, is falsely accused of William's murder. The true murderer is in fact the Monster, whom Victor created and therefore feels responsible for:
But I, the true murderer, felt the never-dying worm alive in my bosom, which allowed of no hope or consolation.
Victor feels so guilty that he goes so far as to call himself a murderer. The "worm" Victor describes represents his knowledge of the truth, a knowledge that is active and restless. This metaphor expresses Victor’s psychological state, one of extreme remorse and suffering and from which he can never gain relief.
The worm is also an allusion to Mark 9:48 in the Bible, which refers to the "worm that never dies" as an expression of the unending torments of hell. Notably, in this Bible passage, Jesus has just been telling his disciples that it's better for a person to cut off the body parts with which they commit sin than to enter Hell physically intact. Though the language is hyperbolic, it conveys the idea that it's preferable to suffer in life than to do terrible things and suffer for them in the afterlife. In using this figurative language, especially by using a biblical allusion that most readers would readily pick up on, Shelley suggests that Victor’s actions have grave moral implications.