John Gardner’s Grendel is a celebrated example of the ontological postmodernist fiction. Along with a discovery of self with which Grendel the narrator of the novel is concerned, grand narratives such as philosophy are questioned. Grendel denies the external objective reality and generously allows the legitimacy of fantastic and non-realistic methods by using “life-affirming fabulous art” as its major technique. Art becomes the central issue related to the question of ontology; it is both presented as the only mediator giving meaning to the futility of life or yet another grand illusion. Philosophical questions are elaborated in the novel through the seminal technique of the amalgamation of a medieval setting with modern concerns (the rewriting of an old English epic). The paper is an attempt to shed some light on the philosophical turn of John Gardner’s novel which, it is argued, is its central postmodern aspect.