sound
SOWND
/saʊnd/
Describes an argument that is both logically valid and contains premises that are entirely true in reality.
This is the gold standard of deductive reasoning: perfect logical structure coupled with indisputable real-world truth.
The story behind the word. Originating from Old English 'sund', meaning healthy or free from defect. Just as a sound vessel has no cracks to leak water, a sound argument has no structural or factual defects to leak truth.
Word relationships
- airtight: Airtight is informal and highlights immunity to criticism; sound is formal and requires structural validity plus factual truth.
- unsound: Lacking either logical validity or truth in its premises.
Commonly confused with
- valid: An argument can be valid with false premises, but it can only be sound if the premises are true.
Word family
- soundness (noun): The state of being structurally valid and factually true.
Collocations
- sound argument
- sound judgment
- sound reasoning
- factually sound
Idioms & expressions
- safe and sound
- of sound mind
Example sentences
- "A deductive argument is sound if and only if it is valid and all its premises are actually true." Philosophy of Science
- "The auditor confirmed that the company's risk mitigation strategy was built on sound logical foundations." Financial Strategy
Memory hook
SOUND reasoning is HEALTHY reasoning—no cracks in logic, no lies in premises. Valid logic + True premises = Sound argument.
When not to use
Do not confuse with audio sounds, or casual uses like 'sounds good'. In logic, it has a precise technical meaning.
Fun facts
- The phrase 'safe and sound' uses this exact ancient Germanic root meaning 'uninjured and intact' rather than noise!
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