The epic is, in the seventeenth and eighteenth centuries, one of the genres codified most drastically by neoclassical poetics, whereas early modern epics are systematically divided into cantos (or books). It may therefore come as a surprise that such divisions are not the object of theoretical attention, in striking contrast to the divisions of dramatic works (acts and scenes), which are considered the primary instruments of dramatic dispositio. This study presents this manifold theoretical loophole, taking Diderot’s definition of the “Chant” as its starting point, and going back the classical sources of the early modern neo-Aristotelian critical tradition. The epic canto (or book) appears to be an heterogenous textual segment, partaking both from a material and a narratological definition of epic dispositio.