Two major astrological works that survive from the second century CE, Claudius Ptolemy's Tetrabiblos and Vettius Valens' Anthologiae, display certain notable differences of approach and conceptual framework. These differences may serve as the starting point for any inquiry concerning both the contemporary mentality and fundamental assumptions which shaped the development and transmission of astrology in the relevant period. 3 H. Diels (Berlin, 1879); it is important to note that at the turn of the last century the underlying pattern of his Doxographi was challenged in the comprehensive study of J. Mansfeld and D. Runia, Aëtiana. The Method and Intellectual Context of a Doxographer (Leiden, 1997). The inconsistencies of Alcinous' Didascalicus were extensively studied by T. Göransson in Albinus, Alcinous,