Percy Bysshe Shelley wrote the Preface to Mary Shelley's Frankenstein in September 1817. It immediately alludes to a "Dr. (Erasmus) Darwin," which gives some medical and scientific credence to the novel that it might not have had. Percy Shelley also mentions the German philosophical writers who, at the time, were experimenting with novels that touched on the Gothic genre, the science fiction genre, and the medical genre. Percy Shelley attempts to put Frankenstein in the context of other novels. He does not want the novel to be just a "mere tale of spectres." Wishing for us to suspend our disbelief that the dead can be brought back to life, he sees this as a novel that is more universal in nature and that gives insight into the human condition.
Shelley aims to seek the "truth of the elementary principles of human nature" and supply some innovative ideas regarding those simple human truths. The allusion is to the age of Romanticism and the Gothic novel. Romantic novels concern themselves with passion, not reason, and imagination and intuition, rather than the logical. Gothic novels frequently deal with the supernatural and remote, far away settings. Frankenstein will not be different and will adhere to the simple rules of Gothic novels. Shelley invokes the great works of Greek and English literature to act as guides and as a guideline for this work. He cites Homer's The Iliad, Shakespeare's Tempest and Midsummer Night's Dream, and Milton's Paradise Lost as works that are worthy of imitation and serve as exemplary models. He hopes that Frankenstein contributes to the body of English and world literature, perhaps equaling those previously mentioned works.
Shelley tells briefly how the novel came into being. During the wet and cool summer of 1816, in Geneva, Switzerland, several friends gathered to create and tell ghost stories. Percy Shelley mentions himself, Lord Byron, and Mary. He omits mention of Byron's mistress, Claire (Jane) Clairmont and of another guest, John William Polidori. Polidori later published his own Gothic novel, The Vampyre; a Tale (1819). This summer meeting produced two of the most important characters of English literature: the Frankenstein monster and the Vampire.