The prologue to the treatise tells us that human skill, a gift given by God, should be directed toward the His service, and that failure to make use of such a skill as granted by God is both lazy and foolish. Moreover, beautiful and precious objects are not to be despised but to be appreciated in and of themselves, for God has provided the materials on this earth with which to make them. Interestingly, Theophilus describes which countries were best known for certain arts: Greece for its many colors of paint and mosaics, Russia for niello, Arabia for repoussé, cast work, and engravings, Italy for its gilt vessels, gem, carving and ivories, France for windows, and Germany for metal, wood, and stonework. Finally, it should be noted that Theophilus emphasizes his own humility both literally in the prologue as a monk "of many" in the service of God, in the manner in which he leaves his specialization toward the last part of the book, and insofar as he asks that those who use the manual pray especially for God's mercy.
Primary source:
Theophilus, The Various Arts De Diversis Artibus, ed. and translated by C.R. Dodwell, Oxford, 1986.
Comparanda:
Roger of Helmershausen reliquary: in Hermann Deckert, ed. Religiöse Kunst aus Hessen und Nassau, vol. II, no. 157, and vol. III plates 245b-250, and plates 240-45a.
Censer: Tonnochy, "A Romanesque Censer-cover in the British Museum" Archaeological Journal vol. LXXXIX 1933, pp. 1-16.
Theophilus:
prologue: pp. 1-4 (Latin and English)
Book II: i-ix, xvii-xxix for stained glass
Book III: LIV for enamels
Book III: XXVI-LVII for chalice
Book III: LXI-LXIII for the cast censer