Soundness

Cogito ergo sum Logic and rhetoric

Key articles

Logical fallacy Syllogism Argument

General logic

Appeal to emotion False dilemma Fallacy of opposition Negative conclusion from affirmative premises Escape to the future Argument from incompatible attributes

Bad logic

Nazi analogies Fallacy fallacy Bulverism Hindsight bias Affirming the consequent Viés de seleção v - t - e

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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.

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