Use parallel structure across every level of the pyramid

Ideas at the same level of the hierarchy should be grammatically and logically parallel.

Why it works

Parallel structure signals to the reader that the items at a given level belong to the same category and carry equal weight. Non-parallel items force the reader to perform additional categorization work ("which of these is a sub-point and which is a peer?") that consumes working memory and reduces comprehension. The brain uses parallel grammar as a structural cue; violating it breaks the implicit hierarchy.

How to do it

1. At each level of your outline, check that all items begin with the same grammatical form (all nouns, all verb phrases, all questions).
2. If one item cannot be made parallel, it is probably at the wrong level or belongs in a different branch.
3. Test with the "so what" check: if you list three points, they should all answer the same "so what" question at the parent level.
4. Revise the parent claim if it cannot be supported by all three parallel points without stretching.

Evidence

Parallel structure is a standard principle in rhetoric and technical writing with a long history. Cognitive research on list processing supports the premise that violations create processing friction; direct studies on its use in business documents are sparse. (mechanistic)

Over-applied, parallel structure produces stilted, formula-like prose. It is a discipline for logical organization, not a style goal.

Common mistake

Making items syntactically parallel ("do X, do Y, do Z") while leaving them logically non-parallel — X is a tactic, Y is a principle, Z is a caveat — which creates false visual symmetry.