Secundum quid

Meaning "[what is true] in a certain respect and [what is true] absolutely".

What often happens here is that the general rule being used is either assumed to have a wider scope (being more general) than is reasonable, or that it is simply mismatched with the case that it is being used to cover.

We have a deep need to explain things that happen, which leads to many people accepting a general rule as explanation for a specific case, even when that rule clearly does not apply. A convenient Secundum quid may thus be used deliberately when there is no general rule available.

Secundum quid 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. The expression misuse of a principle can be used as well.

Instances of secundum quid are of two kinds:

1. Accident — a dicto simpliciter ad dictum secundum quid (where an acceptable exception is ignored) [from general to qualified]
   Example:
   "Water boils at a temperature of 100°C/212°F. Therefore boiling water will be hot enough to cook an egg hard in 5 minutes".
   At 1500m/5000 feets the water boils at 95°C/202°F. The eggyolk will still be running after 5 minutes.
2. Converse accident — a dicto secundum quid ad dictum simpliciter (where an acceptable exception is eliminated or simplified) [from qualified to general]
   Example:
   "Let me tell you: all great composers die young. Take Mendelssohn: he was 38. Or Mozart, just 35. And Schubert! Hundreds of songs, and he was only 31."
   The arguer cites only the cases that support his point, conveniently omitting Bach: 65, Beethoven: 56, Brahms: 63.