My paper “Formal and Proper: Substantial Form and Essential Accidents in Thomas Aquinas” has been accepted by the American Catholic Philosophical Quarterly. I take the same position about formal causality and essential accidents/properties as David Oderberg does. He does not make a historical case for the position, but I show that our shared view was also that of St. Thomas Aquinas. The abstract is below. If you would like a copy, please email me.
Abstract: Aquinas, following Aristotle, distinguishes between substances and their accidents, that is, between things and their attributes. He also distinguishes between proper accidents (also known as properties in Scholastic terminology) and accidental accidents, that is, between accidents that belong to a substance in virtue of what it is, and accidents that belong to it due to extrinsic factors. Aquinas says that a thing’s proper accidents are caused by the thing’s own principles. John Wippel interprets Aquinas as holding that a substance efficiently causes its own proper accidents. I argue that Aquinas is more plausibly read as holding that a substance formally causes its own proper accidents. Formal causality extends to more than just the informing of matter. Formal causality is a principle of determination: being a certain substance involves the determination of having certain proper accidents.