Reason Diminished examines "the power that wonder wields over reason in [Shakespeare's] late plays, both philosophically and dramaturgically." Peter Platt posits that, in these famous plays, wonder and the marvelous are assigned preeminent positions over reason and order. In fact, Platt argues that the marvelous played a crucial role in Renaissance culture as a whole.

The book opens by surveying theories of wonder from Aristotle's Poetics and Metaphysics through the writings of Renaissance theorists. A crucial chapter examines the many ways that the Renaissance attempted to bring the marvelous to bear on the world around it. The next two chapters look at the tension between realism and the marvelous in Elizabethan fiction and the theatrical tradition of the masque.

Part of the book examines the role of wonder and the marvelous in Shakespeare's romances: Pericles, Cymbeline, The Winter's Tale, and The Tempest. "Shakespeare's 'romances'" writes Platt, "represent various experiments with the marvelous." Platt argues that "late Shakespeare ... invites the spectators to engage in - and in some cases to shape - the marvels on the stage before them.".

A persuasive and resourceful study of some of Shakespeare's most celebrated works, Reason Diminished will add significantly to the ongoing reassessment of Shakespeare's plays and the world in which they took shape.