Diagnostic module
The problem with assumptions
Every untested belief adds risk to the stage above it.
Assumption-led teams usually assume
- The problem exists because it feels logical.
- The solution is wanted because early conversations sound positive.
- The market is large enough because reports say so.
Diagnostic module
Evidence and verdict rules
Strict inputs only. Missing proof does not receive interpretation credit.
What counts as evidence
- Verifiable source material from real users.
- Observed behaviour, stated preference, or measurable outcome.
- Evidence tied to the actual stage decision being made.
What scores zero
- Paraphrased summaries with no source proof.
- Belief, intuition, or internal alignment.
- Projected future behaviour with no observed history.
Diagnostic module
The Product Fit Cascade
The order matters because each stage depends on the proof below it.
Run the stages in order
- Problem–Solution Fit before Product–Market Fit.
- Product–Market Fit before Business Model Fit.
- Business Model Fit before scale confidence.
Diagnostic module
The validation loop
ProductBooks is not one pass. It is a repeated diagnostic loop.
Loop
- Evaluate.
- Identify what still fails.
- Generate the missing evidence.
- Re-evaluate before moving up.
Diagnostic module
Getting started
Start at the earliest stage you can prove, not the latest stage you want to claim.
Use this rule
- No problem proof: start with Problem–Solution Fit.
- Users exist but pull is unclear: start with Product–Market Fit.
- Growth decisions are near: run Business Model Fit.