Final answer:
An invalid use of the instrument in argumentation refers to a fallacy where the conclusion does not logically follow from the premises, exemplified by a non sequitur.
Step-by-step explanation:
An invalid use of the instrument occurs in argumentation when the logic or reasoning used to arrive at a conclusion does not logically follow from the premises. A classic example of this would be a non sequitur, where the conclusion does not logically follow from the premises, even though the premises themselves might be true.
Example:
Premise 1: All humans are mortal.
Premise 2: Socrates is a human.
Conclusion: Therefore, all mortals are humans.
The premises are true, but the conclusion wrongly asserts a reciprocal relationship that is not supported by the premises. This is a clear case of invalid reasoning.