Soundness

In deductive logic, soundness is a property of arguments importantly related to validity. An argument is valid if and only if it is impossible for the conclusion to be false while the premises are true (i.e. the conclusion must follow from the premises), but an argument is sound if and only if it is valid and its premises are actually true.

Cogito ergo sum Logic and rhetoric

Key articles

Logical fallacy Syllogism Argument

General logic

Appeal to probability Causality Fallacy of accent Moral equivalence Presupposition Tu quoque

Bad logic

Appeal to consequences Damning with faint praise Not as bad as Pathos gambit Release the data Weasel word v - t - e

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Note that an argument can be valid without being sound. Take for example:

P1: If someone knows and employs logic and scientific reasoning, then they do not propagate woo.

P2: Deepak Chopra knows and employs logic and scientific reasoning.

C: Therefore, he does not propagate woo.

The inference from P1 and P2 to C is valid (affirming the antecedent) and thus the argument is valid. However, because P2 is false, the argument is not sound.

See also

• Informal fallacy, a.k.a., soundness fallacy
• Sound science