Alchemy is a highly complex and paradoxical ‘system’ of thought. On the one hand, it ushers in the new Age of the Enlightenment, since it refutes scholastic philosophy and develops an experimental attitude towards nature and reality, with which many members of the New Science – among them, Isaac Newton and Robert Boyle – could easily sympathize. On the other hand, alchemy reveals the contours of an idiosyncratic doctrine based on a melange of myths, biblical quotations, vulgar errors, and speculations. With its endeavour to produce gold (chrysopoeia), its belief in immortality, and its search for the philosopher’s stone, alchemy builds castles in the air, which in the eyes of many eighteenth-century philosophers were absurd. It is precisely this grotesque aura of alchemy that interests a satirist like Jonathan Swift. Although he detested alchemy and its garrulous representatives such as Artephius, Thomas Vaughan, and Elias Ashmole, he was fascinated by the preposterous ideas of these ‘occult writers.’ In his most brilliant satire, A Tale of a Tub (1704), Swift imitated the language and thought of both alchemists and Rosicrucians in order to explode ‘gross corruptions’ in religion and learning. Whereas Swift lavishes abuse on Peter, the representative of Catholicism, and Jack, the spokesman of Puritanism, whom he associates with alchemical learning, he widely spares Martin, the representative of Anglicanism, who has been regarded as the satirical norm. This paper shows that alchemy is a strong force in the field of semantic gravitation.