 The tradition of authors of works in the doxography of physics begins with Aristotle’s pupil and successor Theophrastus. In the catalogue of his oeuvre preserved in his Life in Diogenes Laertius a treatise is listed of ‘Physikôn Doxôn, sixteen books’. For the Greek title in the nominative one has a choice between Physikôn Doxai (‘Tenets of the Natural Philosophers’) and Physikai Doxai (‘Tenets in Natural Philosophy’). Usener and Diels opted for the first alternative, but in the opinion of many scholars today the second option is much more plausible. To this treatise they attributed a number of fragments dealing with the principles (archai: Thales’ water, Heraclitus’ fire, etc.) transmitted for the most part by Simplicius, a Neoplatonist commentator on Aristotle of the 6th c. CE. That Simplicius and others explicitly quote from Theophrastus’ Physics, a different treatise, did not bother them. They further posited that a short monograph of Theophrastus, the De Sensibus, dealing with theories concerning the senses and their objects from Parmenides to Democritus and Plato, is a fragment of this treatise as well. The simple fact however that Plato, not first and foremost a philosopher of nature, is treated here on the same level as Democritus and the other natural philosophers (as is also the case in the fragments dealing with the principles) should have made them more hesitant, even within the scope of their own hypothesis, as to the interpretation of the title of the foundational treatise in sixteen books. 