Ideas from 'Locke on Essences and Kinds' by Antony Eagle [2005], by Theme Structure

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9. Objects / D. Essence of Objects / 13. Nominal Essence
Nominal essence are the observable properties of things
                        Full Idea: It is clear the nominal essences really are the properties of the things which have them: they are (a subset of) the observable properties of the things.
                        From: Antony Eagle (Locke on Essences and Kinds [2005], IV)
                        A reaction: I think this is wrong. The surface characteristics are all that is available to us, so our classifications must be based on those, but it is on the ideas of them, not their intrinsic natures. That is empiricsm! What makes the properties 'essential'?
If kinds depend only on what can be observed, many underlying essences might produce the same kind
                        Full Idea: If the kinds there are depend not on the essences of the objects but on their observed distinguishing particulars, ...then for any kind that we think there is, it is possible that there are many underlying essences which are observably indistinguishable.
                        From: Antony Eagle (Locke on Essences and Kinds [2005], IV)
                        A reaction: Eagle is commenting on Locke's reliance on nominal essences. This seems to be the genuine problem with jadeite and nephrite (both taken to be 'jade'), or with 'fool's gold'. This isn't an objection to Locke; it just explains the role of science.
Nominal essence mistakenly gives equal weight to all underlying properties that produce appearances
                        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.
                        From: 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.
26. Natural Theory / B. Natural Kinds / 4. Source of Kinds
Kinds are fixed by the essential properties of things - the properties that make it that kind of thing
                        Full Idea: The natural thought is to think that real kinds are given only by classification on the basis of essential properties: properties that make an object the kind of thing that it is.
                        From: Antony Eagle (Locke on Essences and Kinds [2005], II)
                        A reaction: Circularity alert! Circularity alert! Essence gives a thing its kind - and hence we can see what the kind is? Test for a trivial property! Eagle is not unaware of these issues. Does he mean 'necessary' rather than 'essential'?