A field guide to the ways reasoning breaks
Broken structure
Also called Illicit process of the major term
Drawing a conclusion about all of a category from a premise that covered only part of it.
All cats are mammals; no dogs are cats, so no dogs are mammals.
Check whether the premise really covered every member of the term in the conclusion.
One of the two classic distribution errors in categorical syllogisms. 'Illicit' marks that the major term — the term in the conclusion's predicate — is claimed about its whole class in the conclusion even though the premises only talked about part of it. It is the structural twin of the illicit minor.
All managers are accountable for the budget; no intern is a manager; so no intern is accountable for the budget — while interns sign for petty cash every week.
All certified auditors may sign off on the report; she is not a certified auditor; so she may not sign — overlooking the partner who co-signs.
All encryption keys are stored in the vault; this token is not an encryption key; so it is not in the vault — and it is.
All senior staff have building access; contractors are not senior staff; so contractors can't enter the building — said at the door where they badge in daily.