Full Idea
A property P is an essential property of an object x iff x could not exist and lack P, that is, as they say, iff x has P at every world at which x exists.
Gist of Idea
A property is essential iff the object would not exist if it lacked that property
Source
Graeme Forbes (In Defense of Absolute Essentialism [1986], 1)
Book Reference
'Midwest Studs XI:Essentialism', ed/tr. French,Uehling,Wettstein [Minnesota 1986], p.3
A Reaction
This immediately places the existence of x outside the normal range of its properties, so presumably 'existence is not a predicate', but that dictum may be doubted. As it stands this definition will include trivial and vacuous properties.
Related Ideas
Idea 13805 Properties are trivially essential if they are not grounded in a thing's specific nature [Forbes,G]
Idea 11993 Jones may cease to exist without some simple property, but that doesn't make it essential [Kung]
Idea 13797 The loss of an essential property means the end of an existence [Elder]