In view of the fact that Chalcidius, the author of the Latin commentary on the Timaeus, falls within the period dominated by neo-Platonism, it is perhaps only natural that he has sometimes been regarded as a member of this school. Thus Baeumkerl and Praechter2 place him among the neo-Platonists of the West along with Macrobius and Boethius. More recent is Eduard Steinheimer's3 effort to prove the neo-Platonic character of the commentary and to show that in certain sections Chalcidius' source was Porphyry. While I am in complete agreement with Steinheimer's arguments against the conclusion of Switalski4 that Chalcidius' source is Posidonius' commentary on the Timaeus, I find his own reasoning in behalf of the use of a neo-Platonic commentary so unsatisfactory that I desire to reopen the question. We shall have little occasion to discuss the mathematical, musical, and astronomical material which forms a large part of the first one hundred and eighteen chapters of Chalcidius. Hiller5 and Switalski have shown from resemblances to Theon of Smyrna that most of this comes from the commentary of Adrastus upon the Timaeus. In chapters 21-22 Chalcidius sets forth the theory which assigns three qualities to each element. It seems that the only parallels to this are Nemesius (De natura hominis 5) and Proclus (In Timaeum ii. 40). Arguing from these parallels Steinheimer, following Krause,' regards it as probable that Chalcidius is following Porphyry. There appears to be no evidence to indicate where or when this theory of the elements arose. If it were the property of any one of his pre-