Secundum quid

Secundum quid (also called secundum quid et simpliciter, meaning "[what is true] in a certain respect and [what is true] absolutely") is a type of informal fallacy that occurs when the arguer fails to recognize the difference between rules of thumb (soft generalizations, heuristics that hold true as a general rule but leave room for exceptions) and categorical propositions, rules that hold true universally.

Since it ignores the limits, or qualifications, of rules of thumb, this fallacy is also named ignoring qualifications or sweeping generalizations. The expression misuse of a principle can be used as well.