The Book of Causes, a Neoplatonic text that originated in the 9th century in Baghdad, was translated into Latin in the 12th century and was initially attributed to Aristotle, is one of the central philosophical texts studied at universities in the 13th century. Its anonymous author develops an ontology inspired by Proclus, but modified in favor of the creation theology of monotheistic religions. The commentary serves as an important source for insights into the origin and content of the book. It also illustrates the working methods of one of the greatest thinkers of the Latin Middle Ages and is a crucial component for understanding the philosophical and theological work of Thomas Aquinas, who frequently references the Book of Causes.