Jack C. Marler (Ph.D., Toronto, 1988) works closely with the Vatican Film Library to conduct his paleographic research. His interests are late ancient and early medieval philosophy, ancient philosophy, medieval philosophy, modern logic, neoplatonism, medieval spirituality, and western and Byzantine manuscripts. His significant publications include:

• The Mirror of Simple Souls by Margaret Porette, translated, edited, and archivally treated in collaboration with Edmund Colledge and Judith Grant (Notre Dame Press, 1999)
• "The Dialectical Use of Authority in the Periphyseon" in Eriugena: East and West, (ed.) Bernard McGinn (Notre Dame Press, 1994): 95-113
• "Proclus on Causal Reasoning: I Alcibiades and the Doctrine of Anamnesis" Journal of Neoplatonic Studies 1 (1993): 1-33
• "A Meister Eckhart Autograph?" in collaboration with Edmund Colledge, Scriptorium 36 (1983): 90-5
• "Tractatus magistri Johannis Gerson de mistica theologia: St. Plten, Diöezesanarchiv MS 25" in collaboration with Edmund Colledge, Medieval Studies 41 (1979): 354-86.
• He is assistant editor (ex officio) of The Modern Schoolman.