My assessment of Emma Gilby's book is colored—perhaps even distorted—by the disjunction between the promise of its title and its actual contents. By “Descartes's fictions,” I was primed for discussion of the ways in which Descartes's writings incorporate fictional narratives as an integral part of his philosophical enterprise. There is indeed a great deal to talk about in this connection. We meet the many thought experiments that crop up in his work. The hypothesis of the evil genius is the most memorable, but much of Descartes's Le Monde and the corresponding cosmological sections of the Principles can be seen as thought experiments, spinning out the tale of what we would witness were God to create an entirely new universe governed by the same natural laws as the world we empirically inhabit. Descartes expressly calls the setting of this new creation the “imaginary spaces” of natural-philosophical conjecture.

Alongside Descartes's thought experiments stand the pocket narratives embedded in leading metaphors like that of losing one's way in a forest or wandering along uncharted roads in the dark. These narratives include the highly selective autobiography that opens the Discours de la méthode, including the mini-picaresque of his travels as a soldier in Germany and the famous conversion experience in the stove-heated room in a tavern near Ulm; the decision to cast the Meditations in the “analytic” mode of reimagined problem solving rather than in the “synthetic” mode of deducing proofs from a priori principles; Descartes's use of Ignatian spiritual exercises as a model for the sequence of highly imagistic acts of “attention” or mental vision that carries his evolving metaphysical argument; or the series of dreams memorialized in the Olympica. These dreams are arresting not only for the light they shed on the conversion experience of which Descartes saw them as an allegorical commentary, but also for the fact that they embody all of the guiding metaphors of Cartesian thought.

Gilby touches on most of these matters, but glancingly—Descartes's dreams, for example, barely figure at all. I suspect the reason lies in uncertainty as to how to unpack a second suggestive term in the book's title, “poetics.” I had thought to find close poetological analysis of the forms Descartes's fictions take and of the ways in which those forms condition his natural-philosophical, metaphysical, and ethical arguments and doctrines. Instead, the author mainly focuses on literary conversations taking place in Descartes's intellectual milieu. She reviews debates surrounding the problem of vraisemblance, or verisimilitude, posed by the vogue for tragicomedy in 1620s Paris and the polemics stimulated by the public letters of Descartes's friend Guez de Balzac, together with brief mention of Descartes's own intervention in the quarrel on his friend's behalf. Similarly, in a discussion of Descartes's correspondence with Elisabeth of Bohemia, Gilby considers whether Descartes's moral and metaphysical views prevented him from seeing what contemporaries would have regarded as the genuine philosophical significance of tragic theater. Gilby counters the argument by showing how Pierre Corneille's tragedies of the 1640s end (more or less) happily, thereby supporting Descartes's counsels to Elisabeth on how to turn the tragic happenings in her own life to profitable moral use.

Gilby's commendable desire to anchor Descartes's fictional procedures in period context seems, then, to have eclipsed sustained engagement with Descartes's fictions themselves. One result is a good deal of learned and at times illuminating discussion of issues that are nonetheless tangential to Descartes's enterprise taken on its own terms. Another is a tendency to force matters. Thus, in the introduction and chapter 1, Gilby tries to align Descartes's strictures on the need for steely eyed attention in philosophical thought with Jean Chapelain's views on the role verisimilitude plays in holding readers’ and spectators’ attention to the often credulity-straining events portrayed in prose romance and tragicomic drama. It is true that attention is involved in both cases. However, where Descartes points to the intense mental self-discipline demanded by the philosophical search for truth, Chapelain worries about the risk of losing an audience intent on worldly entertainment. Nor is the kind of verisimilitude required to sustain belief in, say, the Cartesian theory of vortices or the ontological proof of the existence of God the same as the kind the willing suspension of disbelief demanded of theatergoers.