Validity and Soundness
Validity of deduction is not affected by the truth of the premise or the truth of the conclusion. The following deduction is perfectly valid:
- All animals live on Mars.
- All humans are animals.
- Therefore, all humans live on Mars.
The problem with the argument is that it is not sound. In order for a deductive argument to be sound, the deduction must be valid and all the premises true.
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Famous quotes containing the words validity and, validity and/or soundness:
“It does not follow, because our difficulties are stupendous, because there are some souls timorous enough to doubt the validity and effectiveness of our ideals and our system, that we must turn to a state controlled or state directed social or economic system in order to cure our troubles.”
—Herbert Hoover (1874–1964)
“There are ... two minimum conditions necessary and sufficient for the existence of a legal system. On the one hand those rules of behavior which are valid according to the system’s ultimate criteria of validity must be generally obeyed, and on the other hand, its rules of recognition specifying the criteria of legal validity and its rules of change and adjudication must be effectively accepted as common public standards of official behavior by its officials.”
—H.L.A. (Herbert Lionel Adolphus)
“Not only our future economic soundness but the very soundness of our democratic institutions depends on the determination of our government to give employment to idle men.”
—Franklin D. Roosevelt (1882–1945)