 Theophrastus discussed the first principles of nature not only in his Metaphysics, but also in his various treatises on natural philosophy; there are passages from Simplicius’ and Philoponus’ commentaries on Aristotle’s Physics (frs. 144A–B FHS&amp;G), which suggest that physics, according to Theophrastus, is just as much concerned with the first principles of nature as with its causes and elements. Many titles of Theophrastus’ works on natural philosophy are mentioned in our sources, e.g., Physics, Opinions of the Natural Philosophers or Opinions in Natural Philosophy, On Nature, On the Heavens, Meteorology, though it is difficult to determine from their few surviving fragments whether they are collections of doxographical material or whether they present Theophrastus’ own theories (see Mansfeld 1992; Zhmud 2001, 2006: 117–65). But even in his role as a doxographer, Theophrastus seems to have been careful in expounding accurately the physical doctrines of his predecessors, and presumably more careful than Aristotle, whether he agreed with them or not (see McDiarmid 1953; Schofield 2002).