A reader, following my post on haecceity:

Mr. Derbyshire—The idea of ‘thisness’ is important. The only difficulty with ‘haecceity’ is that scholastic philosophers thought that everything had to be defined as an intersection of concepts, so to get ‘this man’, you need to combine the concepts of ‘man’ and ‘this’. 20 th century philosophers came up with a more sophisticated framework, in there are still concepts like ‘man’ (which denote sets), but where ‘this’ plays a very different logical role: it’s a deictic term that takes its meaning from context. So there’s no general concept of ‘this-ness’, just individual uses of the word ‘this’ to refer to individuals. It’s a lot like a name: we have no need for concepts of ‘John-ness’ or ‘Derbyshire-ness’, just a convention under which we use those names to refer to certain people. I f your interest in math extend to modal logic, try the works of Richard Montague for a rigorous example of this kind of analysis.

[Derb] Er… I’m going to pass on that. And apparently my new project to slip the word “haecceity” into an otherwise perfectly ordinary sentence may be doomed, doomed.