Soundness; legal strength or force.
- Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874. (noun) (n.) (noun)
The state or quality of being founded on fact; soundness; justness; legality.
- The Winston Simplified Dictionary. By William Dodge Lewis, Edgar Arthur Singer. Published 1919. (noun) (n.) (noun)
Validness; strength or force to convince; justness; soundness; legal strength or force.
- Nuttall's Standard dictionary of the English language. By Nuttall, P.Austin. Published 1914. (noun) (n.) (noun)

Usage examples:

As a man is always in danger of talking nonsense in dealing with a subject concerning which his knowledge is superficial, I shall not undertake to pronounce upon the validity of the theory which is here advanced.
- Essays on Scandinavian Literature by Hjalmar Hjorth Boyesen
And hasn't the person convinced himself of the validity of his present state?
- A Practical Guide to Self-Hypnosis by Melvin Powers
To many of the difficulties of fiction, as we have seen, it brings precisely the right instrument; it gives validity gives direct force to a story, and to do so is its particular property.
- The Craft of Fiction by Percy Lubbock