Aristotle's "De Anima" was all about creating a third option for analyzing natural phenomena that didn't rely on either the sophists / pyrrhonists slipperiness or any kind of metaphysical essentialism. This breezy pluralism is what has proven attractive to many people even since we've learned that the atomist metaphysicians were, in fact, correct all along.
One of the standard challenges to the definition of any living thing would be eating: a deer, say, survives by eating grass. ...