Consider the sentence
Rationalism has many followers.
What in principle looks like a rather dull N+V+O statement does not however allow for seeminlgy innocuous variations on the object:
*Rationalism has many people.
The reason why the former is valid while the latter is not is that followers are followers of something, in this particular case rationalism:
Rationalism has many followers [of rationalism].
In fact, we can view our sentence as a mere rewording of:
There are many followers of rationalism,
which leads us to hypothetize the existence of the following syntactic transformation:
There is/are [Det] N of NP → NP has/have [Det] N.
There were lots of fans of the Beatles → The Beatles had lots of fans.
There are no enemies of Rome → Rome has no enemies.
This transformational rule explains from a purely syntactical perspective why superficially similar sentences like *Rationalism has many people are invalid --they have no "There is..." equivalent.
Interestingly, the rule seems to operate in other languages apart from English (I presume that at least in most modern European languages):
El racionalismo tiene muchos seguidores.
Le rationalisme a beaucoup d'adeptes.
Rationalismus hat viele Anhänger.
This points to some general (maybe universal?) mechanism of reification of the possesion relationship between nouns.