 Cicero often refers to Theophrastus together with Aristotle in matters of ethics, politics and rhetoric. Although he gives Theophrastus a subordinate role, he regards the encyclopedic research carried out by him as a guide containing useful directives to politicians and rhetoricians, but also as a helpful example in his attempt to present Greek philosophy to the Roman society (see Gigon 1988; Runia 1989; Fortenbaugh 2005). The encyclopedic character of Theophrastus’ writings, and in particular of his treatise Opinions of the Natural Philosophers or Opinions in Natural Philosophy, has also been assumed to be the source for much of the material on the Presocratics in later doxographic accounts. In his seminal work Doxographi Graeci (1879), Hermann Diels argued that doxography proper began with the Theophrastean writings; according to him, the fragmentary information on the Presocratics found in his reconstructed Aëtius’ Placita (1st/early 2nd cent.), though debased and modified in the course of transmission, is linked to Theophrastus’ treatises in a direct and vertical line of descent. He further argued that also a number of doxographical passages in Hippolytus’ Refutatio Omnium Haeresium (early 3rd cent.), in Diogenes Laertius’ Lives (early 3rd cent.), in the Stromateis preserved by Eusebius (early 4th cent.) and in a few other works of minor importance, in some way or other for the most part go back to Theophrastus himself. By and large Hermann Diels’ argument as pertaining to Aëtius, though in need of revision, has been judged as correct; but the relation of the doxographical sections in the person-oriented overviews of the later authors to the topic-oriented work of Theophrastus seems to be more complicated than he believed. Moreover, Diels has also been criticized for having failed to take into account the possibility that already before Aëtius more than a single tradition existed, or mutually diverging witnesses belonging to the same tradition may have been available (see Mansfeld 1992, 1998).