Full Idea
An individual essence or haecceity is a narrower type of individual concept. This is a property which is had necessarily, and which it is impossible for any other thing to have.
Gist of Idea
A haecceity is a property had necessarily, and strictly confined to one entity
Source
Roderick Chisholm (Person and Object [1976], 1.4)
Book Reference
Chisholm,Roderick: 'Person and Object' [Open Court 1976], p.29
A Reaction
[Apologies to Chisholm for leaving out the variables from his definition of haecceity. See Idea 15802] See also Idea 15805. The tallest man is unique, but someone else could become the tallest man. No one else could acquire 'being Socrates'.
Related Ideas
Idea 15805 Being the tallest man is an 'individual concept', but not a haecceity [Chisholm]
Idea 15802 I use variables to show that each item remains the same entity throughout [Chisholm]