The quality or state of being sound; as, the soundness of timber, of fruit, of the teeth, etc.; the soundness of reasoning or argument; soundness of faith.
- The state or quality of being sound.
- The result or product of being sound.
- The property (of an argument) of not only being valid, but also of having true premises.
- The property of a logical theory that whenever a wff is a theorem then it must also be valid. Symbolically, letting T represent a theory within logic L, this can be represented as the property that whenever is true, then must also be true, for any wff φ of logic L.