Definition of "soundness" [sound•ness]

• The state or quality of being sound. (noun)
• The result or product of being sound. (noun)
• The property (of an argument) of not only being valid, but also of having true premises. (noun)
• 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. (noun)

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• "What will it take for markets to be convinced of the long-term soundness of European public finances?"
• "The community's, i.e. Cherokee's, financial soundness is a result of low expenditures and a very high soldier's retirement, he says."
• "This example confirms what we know about argument: logical/formal soundness is important, but the biases that audiences bring to the table are equally important — because the success of an argument ultimately depends on whether or not it actually persuades."