Refusal to Guess. The design rule that missing required information must become visible state instead of invented input, assumed context, or confident prose.
Refusal to guess is Law V in operational form. When a system lacks the facts needed to recommend, approve, route, or execute consequential work, the honest behavior is to ask, block, downgrade, or decline. It does not fabricate a budget, contact, evidence source, policy result, or approval just to keep the workflow looking complete.
A data-request blocker is one concrete mechanism for this rule: the missing fact gets an owner, dependency, and resolution path. Ungrounded confidence is the failure this rule prevents.