Iamblichus took a clear stand in the late-antique debate on the origin of matter: in his view, matter is generated, in the sense that it is brought about by a higher principle (primary causes) outside physical time. Two passages testify to this conception: In Tim. fr. 38 Dillon (= Procl. In Tim. I, p. 386.8-13 D.) and Ad Porph. (De myst.) p. 196.14-19 Saffrey-Segonds (= VIII3, p. 265.6-10 Parthey). The relation between the two, however, is rather problematic and scholars (...) stand divided: some maintain that Proclus drew the conception expounded in In Tim. fr. 38 from Iamblichus’ commentary by the same title, others that he drew it from Ad Porph. The question is a far from marginal one. It is connected to the problem of the attribution of Ad Porph. and strongly bears upon the issues of Iamblichus’ work method and of his doctrine. Moreover, the very reconstruction of the text of Ad Porph. closely depends on how the analogy connecting it to In Tim. fr. 38 is understood. A reading of the two passages, first each in its own context and then in the light of one another, reveals that In Tim. fr. 38 is based on the lost commentary on the Timeaeus. Consequently, the two passages are seen to adopt a reverse perspective on the subject, so to speak: In Tim. fr. 38 elucidates Plato through Hermes, while Ad Porph. elucidates Hermes by introducing Platonic notions. Finally, with regard to Ad Porph. p. 196.14-19, a suggestion is made to retain the transmitted text. (shrink)