 In addition, we are fortunate to have some information about Theophrastus’ theory of knowledge, mainly thanks to a passage in Sextus Empiricus’ Against the Logicians, in which Sextus presents the different views of preceding philosophers on the criterion of truth (fr. 301A FHS&amp;G). There are many ambiguous statements in this passage, but it clearly ascribes to Theophrastus the view that sensation (aisthēsis) and thought (noēsis) are the sources of knowledge, while self-evidence (to enarges) is the basic criterion for both. So, Theophrastus is said to have claimed that our senses are moved by the sense object and, when the sensation is self-evident, a reliable memory of the sensation and an appearance or an imagination (phantasia) of the sense object follow; for instance, the memory and the phantasia of Socrates existing in the minds of those who knew him directly. A third movement is added, namely rational phantasia, which results from our judgement and choice, and which involves the production of a model by the aggregation of individuals in the universal, for instance the rational phantasia of man; hence, rational phantasia constitutes, with regard to being potential, understanding (dianoia) and, with regard to being actual, intellect (nous). Finally, from understanding and intellect concepts arise, and thus knowledge (epistēmē) and skill (technē). Sextus’ passage has been used as evidence for the interpretation, according to which Theophrastus managed to sort out an ambiguity in Aristotle’s use of the term phantasia, by distinguishing the rational phantasia, which is tied up with speech and reason, from the formation of the phantasia, which is nothing but a by-phenomenon of sensation (see Huby 1989).