Literary Reflexivity
The text of Frankenstein itself symbolizes many of the same themes that its contents symbolize. For example: Frankenstein's monster is a creature created by imbuing various old body parts with a new life; similarly, Shelley's texts include direct quotes and references to many older poems and literary works. The text therefore acts as a composite image of many older stories with "new life" breathed into them, just like the monster.
Creation
The text is virtually obsessed with creation events: Frankenstein creates the monster out of dead tissue; the monster conceives of himself by reading about the creation of Adam in Paradise Lost; the monster asks for Frankenstein to create a mate for him; what's more, three different levels of narrative are actually created: the letters that R. Walton sends his sister, telling of his time sailing to the North Pole; the story that Frankenstein tells Walton, embedded in the letters; and the story that Frankenstein's monster tells Frankenstein of his youth, embedded in Frankenstein's story. The text as a whole, in this way, can be seen as a continual exploration of what is means to create something.
Responsibility
One of the ways in which the text explores the creation event is by posing the question of what responsibility, if any, the creator bears to the created. Frankenstein shuns his monster almost immediately after creating him. The monster attributes blame to Frankenstein for this, and puts the onus on Frankenstein to right his wrongs by creating a mate for the monster. When Frankenstein refuses, the monster punishes him; Frankenstein ultimately comes to believe that it is his duty to kill the monster. The two feel bound to each other by the creation event, and it is this bond that, by the account of Frankenstein and the monster, establishes culpability on the part of the creator for the outcome of the created.
Causal Dependency
The structure of blame in the novel focuses on particular events that are supposed to have completely altered the trajectory of the future -- that is, events that were necessary for broad swaths of future events to have obtained. So, for example, Frankenstein doubts that he would have undertaken the creation of Frankenstein if his father had not scoffed at his son's interest in alchemy and the like (Volume I, Chapter 1). Similarly, the monster blames his creator's neglect and deformed craftsmanship for his own bad lot in life (Volume II, Chapter 7). The reader is thereby invited to question whether this is actually a fair appraisal of causal relation and responsibility.
Promethean Hubris
The alternative title of Frankenstein is The Modern Prometheus, and the story is true to this moniker: in Greek mythology, Prometheus stole fire from the gods and gave it to humanity; he was subsequently bound and punished eternally for his crimes. Similarly, Frankenstein discovered how to give life to things -- a power thought divine -- and is subsequently punished by the endless tragedy delivered unto him by his creation.
Isolation
Isolation manifests both macrocosmically and microcosmically in the novel. The framing narrative is set on a ship sailing to the North Pole, arguably the most isolated point on the globe; more microcosmically, Frankenstein isolates himself from the rest of society by creating life, thereby giving himself a unique status to which no one else can relate; his monster is more directly isolated, because he is the only one of his kind.
Natural Law
The novel poses a question of where the line is drawn between what we can do and what we ought to do. It is shown to be scientifically possible for Frankenstein to create a living being out of dead tissue; yet there is an odd sense of paradox here: though the act seems wholly unnatural, is it not the case that it is natural by virtue of the fact that it can be done? The notion of scientific progress might suggest that Frankenstein was right to create such a being and conduct this research out of interest in expanding humanity's knowledge and mastery over the world; yet the horrific consequences of the experiments suggest that he might be the case that he never should have gone down the path of creating life by himself. This moral puzzle is one of the main issues the novel invites the reader to explore.
