Scholastic Qualities, Primary and Secondary

The distinction between two kinds of qualities, primary and secondary, is one of the core doctrines of Scholastic natural philosophy. Far from being an invention of the modern era, it is something to which any student of Aristotelian philosophy—which is to say anyone who studied philosophy in a European university up until the eighteenth century—would have been introduced at a tender age. The distinction is, moreover, every bit as important for Scholastic philosophers as it would become in the seventeenth and eighteenth centuries, since the primary qualities, on the Aristotelian tradition, are the fundamental causal agents of the natural world. The locus classicus for the Scholastic idea is the beginning of Book II ofOn Generation and Corruption, where Aristotle attempts to tease out the fundamental qualities of the natural bodies around us. Considering Empedocles’s proposal that there are four basic elements—Earth, Water, Air, Fire—Aristotle argues that this thesis can be proved correct by establishing that there are four basic qualities: