object, x, just in case (1) x exhibits P in the actual world and in all worlds in which x exists and (2) there is no possible world where an object distinct from x exhibits P. And some defenders of individual essences (like Plantinga) have followed Leibniz in holding that the haecceity of an object provides a complete concept of that object, a property such that it entails, for every possible world, W, and every property, P, either the proposition that the object in question has P in W or the proposition that it fails to have P in W. Accordingly, they agree that an omniscient being could infer from the individual essence of an object a complete account of the history of that object in each possible world in which it exists.
See also ARISTOTLE , DEFINITION , HAECCE- ITY , MODAL LOGIC , NECESSITY , POSSIBLE WORLD. M.J.L.