The present work deals with ‘Perceforest’, a late medieval text in French recounting the adventures of Alexander the Great and company as they travel and attempt to civilise Britain prior to the advent of King Arthur. Among its most notable features is the great amount of marvels interspersed through the narrative, the encounter with which typically consists in an acute experience of confusion and doubt. The characters of ‘Perceforest’ are deceived by magical illusions, caught in waking dreams, and mesmerised by monsters impressing upon them the constant need to second-guess their perception of reality. A world of uncertainty is thus portrayed, similar to and in dialogue with intellectual movements contemporary to this text’s composition. Drawing on philosophical theories of the second half of the Middle Ages which discussed human cognition in relation to both its particular/subjective and universal/objective capacities, the marvellous essentially provides grounds for a reflection on knowledge, learning, and the surpassing of one’s self, as moral as it is epistemological in that it relies upon principles of personal awareness and responsibility. To encounter a marvel is to discover one’s limits and potential in the pursuit of truth which can be embraced or denied. Readers of ‘Perceforest’ are not exempt from such lessons: their understanding of the events described proves to be equally unreliable, and the result of their own biases. To be sure, the marvellous narrative makes a point of showing how the reading experience is made of one’s necessarily flawed interpretation as much as it is affected by the text. In revealing these inner mechanisms, however, ‘Perceforest’ exposes the inherently fabricated nature of its (and indeed all) diegetic enterprise. With marvels which I shall argue are the privileged tool for the exploration of metafictive concerns, this so-called ‘chronicle’ with claims to historical veracity self-reflects on its status as an artificial product of literature.