Validity

A deductive argument is valid when its form makes it impossible for the premises to be true and the conclusion false.

Also: valid argument, deductive validity, logical validity

What it means

Validity is a property of an argument's form, not of the truth of its premises. If an argument is valid, then whenever all its premises are true the conclusion must be true too. That means a valid argument can have false premises: 'all toasters are made of gold; everything made of gold is a time-travel device; so toasters are time-travel devices' is valid but absurd. Equally, an argument with all true statements can be invalid if its conclusion does not follow. Validity is therefore only half of what makes a good deductive argument; the other half is true premises, which together give soundness. Inductive arguments are judged differently, by strength rather than validity.

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 Not peer-reviewed.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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