Soundness

A sound argument is a deductive argument that is valid and whose premises are all actually true.

Also: sound argument, sound

What it means

Soundness combines two requirements: the argument must be valid, and every premise must in fact be true. Only a sound argument guarantees that its conclusion is true. For example: some states bar people with felony convictions from voting; in those states some professional athletes have such convictions; so in some states some professional athletes cannot vote. Whether an argument is valid is a matter of logical form, while whether its premises are true is a matter of content and evidence. An unsound argument may still happen to have a true conclusion, so showing that someone's argument is unsound does not by itself show that their conclusion is false. The inductive counterpart of soundness is usually called cogency.

The questions it belongs to

• 4.1 Formal LogicWhat makes an argument work, regardless of its subject?
• 4.2.2 Argumentation TheoryWhat does an argument have to do, besides be valid?

Thinkers

• Aristotle

Traditions

• Greek & Roman
• Analytic

To read

• Categories — Aristotle
• Metaphysics — Aristotle
• Nicomachean Ethics — Aristotle

Sources and further reading

• Validity and Soundness (Internet Encyclopedia of Philosophy)
• Deductive and Inductive Arguments (Internet Encyclopedia of Philosophy)

Written by the Coordinates of Thought editors and checked against the sources above on 29 October 2026. Not peer-reviewed. How we write and check.

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