Patriotism that glues together a state is a natural extension of filial piety of a son to his father.
I want to mean the general piety a son feels for his father. Can I say directly "filial piety of son to father"? Or should I say "filial piety of the son to the father"?
the filial piety of a son to his father
You need the definite article preceding the noun phrase, nowhere else. Keep the indefinite article in a son.
a son the typical son, any; not the son, not a certain individual.
Whence,
"the (kind of) filial piety (that) a (typical) son (has) to his father.
Omitting the articles works at least as well as including them. My question would be, Why such absolute determination to exclude the female sex entirely from the picture? For apart from that, the prepositional phrases modifying “filial piety” are redundant.
