Full Idea
Important properties of an object need not be essential, unless 'importance' is used as a synonym for essence.
Gist of Idea
Important properties of an object need not be essential to it
Source
Saul A. Kripke (Naming and Necessity lectures [1970], Lecture 2)
Book Reference
Kripke,Saul: 'Naming and Necessity' [Blackwell 1980], p.77
A Reaction
Kripke's examples are the writings of Aristotle and the actions of Hitler, but these don't strike me as being 'properties' of those people. They are not intrinsic. Kripke, of course, is concerned with how we identify them, not who they actually are.