A field guide to the ways reasoning breaks
Part and whole
Also called Dicto simpliciter, sweeping generalization
Applying a general rule to a case that its rationale was never meant to cover.
Lying is wrong, so never lie to protect someone.
Ask what the rule was for, then check whether this case falls inside that purpose.
One of the thirteen fallacies listed in Aristotle's 'On Sophistical Refutations', the first systematic catalogue of bad arguments ever written. Its Latin name 'a dicto simpliciter ad dictum secundum quid' means 'from a statement made simply to one made in a qualified sense'. The modern reading is narrower than Aristotle's: applying a rule of thumb to a case its rationale does not cover.
Contract terms cannot be renegotiated, so no, we cannot extend a payment deadline for a supplier whose city was hit by an earthquake.
Seatbelts are compulsory on public roads, so the scrapped race car driven on a closed track must have one installed or it cannot compete.
Patients must not be disturbed during consultation hours, so the nurse was written up for interrupting the exam to report a serial number fault on the heart monitor.
Open-plan seating means anyone can take any desk, so the building manager moved the ergonomics workstation assigned by the occupational doctor.