Pliny's Natural History is a peculiar book. The scope of its subject matter and the strangeness of its organising principles are almost unique in surviving Latin literature. But despite its apparent singularity, and despite Pliny's rhetorical insistence on its originality in his preface, there has been very little speculation as to where the Natural History might fit in the landscape of Roman historia. This is partly the result of the traditional marginality of ancient scholarship to Classical studies, but the lack of speculation about the provenance of the Natural History is in large part due to its self-evident but anachronistic recognition as ‘an encyclopedia’. The form and content of the Natural History have been naturalised as markers of an encyclopedic text; it is commonly called ‘an encyclopedia’ within the field of Classics, and maintains an important position in any attempt to trace the history of encyclopedism into antiquity.

Genre has a diffuse influence on the expectations which we bring to the text, and the methods of reading we apply to it. It provides an important framework for understanding the terms on which we should approach the work, suggesting a context for its production or performance and parameters for its content and conclusions. But once we move outside the well-policed genres of ‘high literature’, we can run into difficulties. There has been much debate as to how particular branches of historia demarcate their boundaries; these new studies have been concerned to examine the interactions between different types of prose writing, to discover the disjunctions and continuities between fiction and non-fiction, biography, and history, rhetoric and philosophy.