(fl 4th or early 5th century ce). Translator and commentator. His commentary on Plato's Timaeus (only to 53c) is dedicated to Hosius, long thought to be the bishop of Corduba (d 358). More recently, it has been proposed that the dedication is to a Milanese official of about 395 and that Calcidius was a Christian Neoplatonist active in Milan whose writings were known to St Ambrose. The earliest surviving manuscripts, F-Pn lat.2164 and VAL 293 (formerly 283), date from the early 9th century. Within the tradition of Christian Neoplatonism, Calcidius's commentary made the Timaeus generally (but imperfectly) available to the Middle Ages, although it does not seem to have been known to Macrobius or Isidore of Seville.
Calcidius departs from tradition (in his commentary on Timaeus, 35b) when he asserts that geometry rather than harmonics holds the fundamental position and is a substructure for the others (‘geometrica vicem obtinet fundamentorum ceterae vero substructionis’), but otherwise his commentary is derivative. Several short chapters (40–55; pertaining to Timaeus, 36a–37a) are devoted to Platonic music theory and the World-Soul; at least part of this material is derived either from Theon of Smyrna or directly from Theon's source, Adrastus. The chapters explain the Pythagorean harmonia (6:8:9:12) as it emerges from the duple and triple proportions described by Plato; the story of Pythagoras's discovery of the consonant numbers by suspending weights from strings (paralleling the version in Censorinus, On the Day of Birth, §10), rather than through the more familiar myth of the hammers; the harmonic, arithmetic and geometric means; and the typical numerical characterizations of the 4th, 5th, octave, 11th, 12th, 15th, the tone and the limma. Calcidius, like Gaudentius and Theon, considers the 11th a consonance; this is unusual in a treatise within the Neoplatonic tradition. Having reviewed some of the technicalities of Pythagorean mathematics, Calcidius then comments on Plato's famous image of the two revolving circles of the cosmos and the duality of essence, the Same and the Other (the subject is also related to music by Aristides Quintilianus: On Music, iii.24). By interpreting Plato's creation of the World-Soul in Christian terms, Calcidius attempts to show points of agreement between the Platonic and Christian views of the compound nature of the human being. In chapter 267 (in the section on the use of sight and hearing, with reference to Timaeus, 47d), Calcidius makes explicit the importance of music: ‘Without doubt music rationally adorns the soul, recalling it to its old nature, eventually making it as God the creator made it in the beginning’ (Procul dubio musica exornat animam rationabiliter ad antiquam naturam revocans et efficiens talem demum, qualem initio deus opifex eam fecerat).
Calcidius's commentary is cited in glosses to the De nuptiis Philologiae et Mercurii of Martianus Capella attributed to Johannes Scottus Eriugena and Remigius of Auxerre, and both the Musica and Scholica enchiriadis borrow from it. He is also cited occasionally by later musical writers such as Bernelinus, Engelbert of Admont, Jacobus of Liège and Franchinus Gaffurius. The treatise was first published in 1520.
J.H. Waszink, ed.: Timaeus a Calcidio translatus commentarioque instructus (London, 1962)
E. Steinheimer: Untersuchungen über die Quellen des Chalcidius (Aschaffenburg, 1912)
P. Courcelle: Les lettres greques en Occident, de Macrobe à Cassiodore (Paris, 1943, enlarged 2/1948; Eng. trans., 1969, as Late Latin Writers and their Greek Sources)
J.H. Waszink: Studien zum Timaioskommentar des Calcidius (Leiden, 1964)
P. Courcelle: ‘Ambroise de Milan et Calcidius’, Romanitas et Christianitas: Studia Iano Henrico Waszink A. D. VI Kal. Nov. A. MCMLXXIII XIII lustra complenti oblata, ed. W. den Boer and others (Amsterdam, 1973), 45–53
A. Barbera: The Persistence of Pythagorean Mathematics in Ancient Musical Thought (diss., U. of North Carolina, 1980), 273–6
M. Dunn and C.A. Huffman: ‘The Cheltenham MS. of Calcidius' Translation of the Timaeus’, Manuscripta, xxiv (1980), 76–88
A.K. Holbrook: The Concept of Musical Consonance in Greek Antiquity and its Application in the Earliest Medieval Descriptions of Polyphony (diss., U. of Washington, 1983)
M. Huglo: ‘The Study of Ancient Sources of Music Theory in Medieval Universities’, Music Theory and its Sources: Antiquity and the Middle Ages: Notre Dame, IN, 1987, 150–72
N. Phillips: ‘Classical and Late Latin Sources for Ninth-Century Treatises on Music’, ibid., 100–35
J. Godwin, ed. and trans.: The Harmony of the Spheres: a Sourcebook of the Pythagorean Tradition in Music (Rochester, VT, 1993), 60–63
T.J. Mathiesen: Apollo's Lyre: Greek Music and Music Theory in Antiquity and the Middle Ages (Lincoln, NE, 1999), 616–17
THOMAS J. MATHIESEN