Dicto simpliciter

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 , of rules of thumb, this fallacy is also named ignoring qualifications. The expression misuse of a principle can be used as well.

Water boils at a temperature of 212° Fahrenheit; therefore boiling water will be hot enough to cook an egg hard in five minutes: but if we argue thus at an altitude of 5,000 feet, we shall be disappointed; for the height, through the difference in the pressure of the air, qualifies the truth of our general principle.

Compare with:

All persons are mortal.
Socrates is a person.
Therefore, Socrates is mortal.

The following quatrain can be attributed to C. H. Talbot:

 I talked in terms whose sense was hid,
Dividendo, componendo et secundum quid;
Now secundum quid is a wise remark
And it earned my reputation as a learned clerk.

Instances of secundum quid are of two kinds:

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