Potentiality and actuality are Aristotle’s indispensable modal tools, providing resources for a variety of sophisticated analyses. Notable applications include a nonreductive, “dialectical” interweaving of is and ought that allows conditional “oughts” to be constructed subsuming applicable details of a contextual “is”. This allows something like structural causality to coexist with something like Kantian freedom.
Modern discourse on the relation of “is” and “ought” has generally oscillated between a reductive ethical naturalism that explains “ought” exclusively in terms of “is” on the one hand, and an unexplainable dualism of “is” and “ought” on the other.
With his explicit distinction between modes of potentiality and actuality, Aristotle had a better way. He also talked about the typical modern modalities of abstract possibility and necessity, but concrete potentiality and actuality are the crown jewels of Aristotle’s modal discourse. (See also The Importance of Potentiality.)
The Postmodern Peripatetic 