Book 14 argues that filial child, patriot, saint, and divine child are not held together by raw duty alone. Their marrow is true love. What changes from stage to stage is not the substance but the radius.
That matters because it prevents public morality from becoming mechanical. Patriotism without true love becomes tribalism. Filial piety without true love becomes performance. Even sainthood becomes abstraction if the marrow is missing.
The note also creates a clean link back to earlier love theology in the vault. Love is one reality expressed across different relationships, and Book 14 names the public-hearted forms of that same reality.