Full Idea
Brody bases sortal essentialism on the notion of a property that an individual must possess throughout its existence if it possesses it at any time in its existence. ...'Once an F, always an F'. ...Being a parrot is not a temporary occupation.
Gist of Idea
A sortal essence is a property which once possessed always possessed
Source
report of Baruch Brody (Identity and Essence [1980]) by Penelope Mackie - How Things Might Have Been 7.1
Book Reference
Mackie,Penelope: 'How Things Might Have Been' [OUP 2006], p.119
A Reaction
Hm. Would being less than fifty metres tall qualify as a sortal essence, for a giraffe or a uranium rod? If there is one thing an essential property should be, it is important. How do we assess importance? By explanatory power! Watch this space.