One of the monuments of Peripatetic scholarship which time and the long shadow of Aristotle have concealed from full view, and barred from general acclaim, is “The opinions of the natural philosophers” by his colleague and successor, Theophrastus of Lesbos. The work established the fields of intellectual history in the form of “doxography” in general, and of the history of natural science in particular, as separate branches of study, and laid the foundation for all subsequent research on the Presocratic thinkers and the origins of philosophy. Its pervasive influence and the tradition it generated may be briefly recounted: shortly after the turn of the 1st century B.C. there appeared in the school of Poseidonius a revised and updated edition of the work, which also included the opinions of philosophers posterior to Theophrastus. In the following century the supplemented compilation was edited anew by an otherwise unknown Aetius, under the simple title “Opinions” (Placita). Around A.D. 150 Aetius's edition reappeared in an epitome falsely attributed to Plutarch and bearing the title, “Epitome of the Natural Opinions of the Philosophers” (Placita philosophorum). Of these works, only the last named has survived intact in Greek: its attribution to a famous author and its wide use, especially by Christians in their polemical writings, seem to have contributed to its preservation. One may further hazard the guess that by the same token, and because a tradition of reference to, and respect for, this Placita had been created in Christian circles, it was translated into Arabic by a person in the same tradition, a Syriac Christian of Greek descent, Qusṭā ibn Lūqā (died c. A.D. 912). In Arabic translation it saw the widest diffusion possible among authors interested in ancient philosophy (see the diagram in the work reviewed, p. 88).