Conventional portrayals of Thales of Miletus as the first natural philosopher (phusiologos) often revolve around his materialist cosmology with water as the principle (archе̄) of all things. This article reconstructs a lesser-known and largely lost late ancient tradition that saw in Thales a metaphysician who anticipated a vaguely proto-Neoplatonic theology. It then argues that such late ancient reinterpretations constitute the missing link between the classical image of Thales and his reception in Islamic doxographies, particularly in the Arabic ps.-Ammonius. Thus, by closely examining the Greek and Latin evidence that paved the way for Thales Arabus, this article advances two conjectures: (1) the metaphysically charged reading of Thales predates the advent of the Graeco-Arabic translation movement (and creatively expounds on the Aristotelian evidence), and (2) ps.-Ammonius ultimately relies on a lost Greek Vorlage, preserved through the Neoplatonising (likely Syriac-Christian) currents of late antique apologetics and syncretism.