 Just as medieval thinkers adopted Aristotle’s four inquiries, so too did they adopt his distinction of four types of causes (material, formal, efficient, and final) elaborated in Aristotle’s Metaphysics v.2 and other places. Although Israeli adopts the schema, he notes that within each of the four categories a cause can be either spiritual or corporeal. While a “spiritual material cause” might sound oxymoronic to our ears, in his Book of Definitions Israeli provides an example: