The Five Types of Predicates

Porphyry offers an alternative, and perhaps more general, classification of predicates than the one we find in Aristotle's categories. He focused on the notions that came to be called the five Porphyrian words or expressions: genus, species, specific difference, accident, and property. Every term we use to describe something will fall into one of these five types,. The most familiar are genus and species; what marks out a species from its genus is its specific difference.