Rather than imagining a single concept boundary, maybe try imagining the entire ontology (division of the set of states into buckets) at once. Imagine a really fine-grained ontology that splits the set of states into lots of different buckets, and then imagine a really coarse-grained ontology that lumps most states into just a few buckets. And then imagine a different coarse-grained ontology that draws different concept boundaries than the first, so that in order to describe the difference between the two you have to talk in the fine-grained ontology.
The “unique infinum” of two different ontologies is the most abstract ontology you can still use to specify the differences between the first two.
Rather than imagining a single concept boundary, maybe try imagining the entire ontology (division of the set of states into buckets) at once. Imagine a really fine-grained ontology that splits the set of states into lots of different buckets, and then imagine a really coarse-grained ontology that lumps most states into just a few buckets. And then imagine a different coarse-grained ontology that draws different concept boundaries than the first, so that in order to describe the difference between the two you have to talk in the fine-grained ontology.
The “unique infinum” of two different ontologies is the most abstract ontology you can still use to specify the differences between the first two.