The distinction between essential versus accidental properties has been characterized in various ways, but it is currently most commonly understood in modal terms along these lines: an essential property of an object is a property that it must have while an accidental property of an object is one that it happens to have but that it could lack. Let's call this the basic modal characterization where a modal understanding of a notion is one that explains the notion in terms of necessity/possibility. In the characterization just given of the distinction between essential and accidental properties of an object, the use of the word “must” reflects the fact that necessity is invoked in the elucidation, while the use of the word “could” reflects that possibility...