Definition

Structural rule: the book’s front matter contains two distinct objects, kept separate rather than merged into a single introductory block.

Explanation

The rule exists because front matter tends to collapse into one undifferentiated block if an author doesn’t deliberately hold two objects apart — and once collapsed, each object does its job worse. Whatever the two objects are doing (framing the reader’s entry versus establishing the book’s stance, or a similar split), forcing them into one merged section blurs the distinct function each is supposed to perform before Chapter 1 starts.

Practically, this is a discipline about sequencing intent. A reader moving through front matter should be able to tell which object they’re in and why, the same way [The Love Declaration] and [The Grease Trap] are sequenced deliberately rather than blended into one opening pitch. Front matter that mixes its objects loses the sequencing advantage each one was built to provide on its own.