Full Idea
Nominal essence does not allow for gradations in significance for the underlying properties. Those are all essential for the object behaving as it observably does, and they must all be given equal weight when deciding what the object does.
Gist of Idea
Nominal essence mistakenly gives equal weight to all underlying properties that produce appearances
Source
Antony Eagle (Locke on Essences and Kinds [2005], IV)
A Reaction
This is where 'scientific' essentialism comes in. If we take one object, or one kind of object, in isolation, Eagle is right. When we start to compare, and to set up controlled conditions tests, we can dig into the 'gradations' he cares about.
Related Idea
Idea 19655 Kant says we can describe the categories of thought, but Hegel claims to deduce them [Kant, by Meillassoux]