sound
SOWND
/saʊnd/
Describing a deductive argument that is both logically valid and contains premises that are factually true.
In formal logic, validity is about structure, but soundness requires both perfect structure AND true premises.
The story behind the word. Traces to Old English 'sund', meaning whole, uninjured, or healthy. In philosophy, calling an argument 'sound' means it is healthy at its core—not just built with good form, but grounded in solid truth.
Word relationships
- valid and true: 'Sound' combines both structural correctness and factual truth in a single formal technical term.
- unsound: Unsound describes an argument that has either a structural flaw or at least one false premise.
Commonly confused with
- valid: An argument is valid if its structure holds; it is sound ONLY if its structure holds AND all its premises are true in reality.
Word family
- soundness (noun): The state or quality of being logically sound.
Collocations
- sound argument
- sound reasoning
- logically sound
- sound premises
Idioms & expressions
- safe and sound
Example sentences
- "An argument can be valid without being sound if one of its starting assumptions turns out to be untrue." Formal Logic
- "To persuade a skeptic, your reasoning must be not merely valid in form, but demonstrably sound in fact." Philosophical Treatise
Memory hook
A SOUND argument sits on solid GROUND. Valid form plus true facts.
When not to use
Do not confuse the logical meaning of 'sound' with audio vibrations or deep sleep; in philosophy, it is an exact technical evaluation of an argument.
Fun facts
- The phrase 'sound mind' in legal wills comes from the same root meaning intact and healthy.
Also appears in
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