The overarching objective of this thesis is to examine the reasons why Frankenstein is transhistorically stable---to discover what is common to both the early-nineteenth and early-twenty-first centuries which gives Frankenstein its present-day relevance as a modern myth. I examine the 1818 edition of Frankenstein from an Ecocritical perspective and resituate it within its cultural context which I treat as a textual ecology. This resituation requires that Frankenstein be considered alongside the prose, poetry and philosophy of Percy Bysshe Shelley (1792-1822). To this end I construct a rich Shelleyan paradigm within which I resituate the novel and through which I perform close-readings of key points in the text within a Shelleyan context. Among other conclusions, I show that there is connection between Frankenstein , Alastor , and Plato's Phaedo which indicates that Frankenstein should not be read literally as a Gothic novel any more than The Phaedo should be read literally as a the last words of a condemned man. Both works are profound allegories which require minute examination. Other conclusions are that Shelley was neither an atheist nor a materialist but a Necessarian very much concerned with the cultural transformation from the pre-industrial ethos to Industrialism. I show how the ecocentrism of Necessarianism is opposed to the anthropocentrism of Industrialism and how this conflict is incorporated into Frankenstein . Popular eighteenth-century readings of the mythology surrounding Prometheus and Nemesis are also examined in detail and compared to Frankenstein, or The Modern Prometheus as a modern myth with a modern aetiology.