From the 18th century BCE onward, in the field of extispicy, Mesopotamian diviners began to take on the weighty task of composing treatises, not to say encyclopaedias. The intellectual project, which seems to have begun during or around the reign of Hammurabi of Babylon (1792-1750 BCE), was not a shortlived movement; on the contrary, it was an endeavour carried out over a period of several centuries and conducted with a rigorous scientific method. The term book seems anachronous in our context, since it usually refers to a codex. Mesopotamian literary or learned texts were inscribed on clay tablets. However, as the term book may also refer, more generally, to the materiality of a text or to an intellectual work, it can be used to designate such tablets or collections of tablets, the latest ones being sometimes called eš.gar or iškaru (‘series’) in 1st millennium colophons. In order to understand the purpose of this tremendous intellectual activity, it is necessary to presuppose the existence of important archives.

The process of writing treatises was a complex one and required wide erudition. It consisted, at first, in giving names to the ominous features present on the entrails. The diviners established a distinction between ominous signs associated with anatomical features and those associated with pathological ones. At first glance, the terminology they used appears to designate random or everyday objects. Nevertheless, with some exceptions like martum (‘bitter’, ‘bitterness’) for the designation of the gall bladder, or ubānum (‘the finger’) for the processus caudatus, the vocabulary was borrowed from spheres of knowledge at some remove from anatomo-pathology relation is found between the ominous features and the human and social spheres: for example, padānum (‘the path’), danānum (‘strength’), bāb ēkallim (‘palace gate’), šulmum (‘well-being’), nidī kussi (‘throne base’), nīrum (‘yoke’), šēpum (‘foot’), kakkum (‘weapon’), erištum (‘request’), and so on. As is well known, the designation of a phenomenon is a good indicator of the knowledge one pretends to have about it. The aim of the diviners was to emphasise the strong link between the ominous signs and their associated oracles.

Alongside this work, which reflected an important evolution of the ideas in favour of abstraction, the diviners found themselves confronted with the necessity of classifying their data.