Aetius (philosopher) in Wikipedia
Aetius (Ἀέτιος) was a 1st or 2nd century doxographer and Eclectic philosopher.
None of Aetius' works survive today, but he solves a mystery about two major compilations of philosophical quotes. There are two extant books named Placita Philosophorum and Eclogae Physicae. The first of these is Pseudo-Plutarch and the second is by Stobaeus. They are clearly both abridgements of a larger work. Hermann Diels, in his great Doxographi Graeci, discovered that the fifth-century theologician Theodoret had full versions of the quotes which were shortened in the abridgements. This means that Theodoret had managed to procure the original book which Pseudo-Plutarch and Stobeaus had shortened. He calls this book "Aetiou tên peri areskontôn sunagôgên," and therefore we ascribe the original Placita to Aetius.
Diels claimed that Aetius himself was merely abridging a work which Diels called the Vetusta Placita (because he wrote his paper in Latin; literally, "Older Tenets"). Unlike Aetius, whose existence is attested by Theodoret, the Vetusta Placita is Diels' invention and is generally disregarded by modern classicists, e.g., the 1999 Cambridge History of Hellenistic Philosophy.
Quotes which are ascribed to Aetius in scholarly essays were actually discovered in either the abridgements of Pseudo-Plutarch or Stobaeus, or Theodoret's full quotes in rare cases, or finally one of several ancient authors who provided corrections to misquotes in one of these works.