This entry is a response to this post on Meteuphoric, but I'm also posting it separately here (with some slight modifications).
I'm going to claim that yes, mistaken unifications are much more common than mistaken divisions. But the details matter here; it's not just about "unification" vs. "division". There are multiple ways we can "unify" things.
One way is to put them into a verbal cluster together. The thing is that this is often pretty useless for inference. Clusters aren't interfaces, and trying to make serious inferences from such similarities doesn't really work very well. The fundamental mistake people make here really of course is not thinking that clusters are interfaces but thinking that they're essences -- which goes along with thinking, ah, these are different manifestations of the same underlying phenomenon. Of course, the latter inference is sometimes true, but people make it too often; and, of course, there are no essences. Basically, 37 ways that words can be wrong, etc.
Another way is to say that two things are different manifestations of the same underlying phenomenon, even if they don't resemble each other (e.g. grasshoppers and locusts or water and ice). This of course is a useful thing. I don't think people make this mistake on its own too often; generally they seem to make this mistake as a result of clustering above. It only really becomes a problem of course when you apply one word to the whole thing and start conflating things. Note that this sort of unification while important still doesn't let you make straightforward inferences about one thing from the other.
A third way is to notice (or claim) that two things are isomorphic, that they "implement the same interface". This is useful for inference (within the domain that the isomorphism is valid, of course). But it would be a mistake to, seeing such an isomorphism, then fall back on naïve verbal categories and conclude that the isomorphs share an essence. Because, of course, there are no essences. But this is (roughly) a mistake I see people actually make. Isomorphisms aren't essences or identities, they're isomorphisms. Thoughtless "unification" is still a mistake.
I'm going to claim that yes, mistaken unifications are much more common than mistaken divisions. But the details matter here; it's not just about "unification" vs. "division". There are multiple ways we can "unify" things.
One way is to put them into a verbal cluster together. The thing is that this is often pretty useless for inference. Clusters aren't interfaces, and trying to make serious inferences from such similarities doesn't really work very well. The fundamental mistake people make here really of course is not thinking that clusters are interfaces but thinking that they're essences -- which goes along with thinking, ah, these are different manifestations of the same underlying phenomenon. Of course, the latter inference is sometimes true, but people make it too often; and, of course, there are no essences. Basically, 37 ways that words can be wrong, etc.
Another way is to say that two things are different manifestations of the same underlying phenomenon, even if they don't resemble each other (e.g. grasshoppers and locusts or water and ice). This of course is a useful thing. I don't think people make this mistake on its own too often; generally they seem to make this mistake as a result of clustering above. It only really becomes a problem of course when you apply one word to the whole thing and start conflating things. Note that this sort of unification while important still doesn't let you make straightforward inferences about one thing from the other.
A third way is to notice (or claim) that two things are isomorphic, that they "implement the same interface". This is useful for inference (within the domain that the isomorphism is valid, of course). But it would be a mistake to, seeing such an isomorphism, then fall back on naïve verbal categories and conclude that the isomorphs share an essence. Because, of course, there are no essences. But this is (roughly) a mistake I see people actually make. Isomorphisms aren't essences or identities, they're isomorphisms. Thoughtless "unification" is still a mistake.
