A recurring problem in much critical writing about the Oulipo is a tendency to homogenize the output of the group's writers in order to present a universal poetics of constrained writing. Oulipians rightly bristle at these attempts to oversimplify the group's history, and a useful distinction has been made by Jacques Roubaud, who notes the widening of the group's membership beginning in 1966, when he joined, and postulates that a second era — the “Perecquian era” — of the Oulipo began in 1969, when Georges Perec published La Disparition, his infamous novel without the letter e. This essay looks at the theoretical writing of Italo Calvino over the six-year period from 1967 to 1973 —the years between his translation of Raymond Queneau's novel Les Fleurs bleues and his full election to the Oulipo — arguing that during this time Calvino's own poetics underwent a significant change with regard to the perceived relationship between creativity and constraint. The essay makes its case by analogy with two authors often cited by the Oulipo — the medieval theologian Ramón Llull and the Atomist philosopher Lucretius — between whom Calvino draws a parallel in one of his final works, the undelivered lectures Six Memos for the Next Millennium. It argues, however, that Llull and Lucretius represent two opposing models of combinatorics and that the former encapsulates Calvino's views at the start of the period in question, while the latter neatly exemplifies his later position. The essay also suggests that the trend in Calvino's thought is germane to the distinction Roubaud makes — that Calvino's earlier position is characteristic of the “pre-Perecquian Oulipo,” while his later views are closer to those of his peers among the group's second wave.