Consider these four situations:
- Conflating two things. Conflation is the mistake of thinking that two or more things are the same thing.
- Incorrectly splitting one thing into two things. This is the mistake of thinking that one thing is two or more things.
- Correctly identifying that two things are the same thing.
- Correctly distinguishing two things that used to be thought of as one thing.
The point I want to press upon you is that the situations in the top row are easier or more likely than the situations in the bottom row, due to working memory constraints. An ontology with fewer objects in it is easier to understand, so it's relatively easy for humans to correctly identify that what they thought was two things is actually one thing, and correspondingly, to mistakenly conflate two things into one. Mutatis mutandis, it's hard for people to notice subtle distinctions. And likewise people have low propensity to mistakenly think that one thing is two things.
This is why I see distinction-mongering as such an essential conceptual activity; it goes against the natural inclination to do the opposite.
It goes back to the personality distinction between lumpers and splitters. Some people want wikipedia articles to include everything related to the subject; others want to individuate the various things into their own wikipedia articles. Ever since the list of subtle distinctions I co-wrote, I've become much more of a splitter, seeking distinctions everywhere and never finding them unfruitful. Perhaps this is some sort of boast, like wow guys, look at how many distinctions I can fit in my head. I nevertheless see it as the essential conceptual activity. As Sarah Constantin once said, "science" means "to split".