Soundness is defined as?

• A. When a deductive argument is invalid
• B. When a conclusion follows logically
• C. When a deductive argument is valid and all premises are actually true
• D. When a statement is true

Answer: (C)

Soundness means a deductive argument is both valid and has true premises. Validity ensures the conclusion follows from the premises, but a valid argument can still be unsound if some premise is false. Only when the argument has a correct form and all premises are actually true is it sound. For example, All humans are mortal; Socrates is a human; therefore Socrates is mortal, is sound because the form is valid and the premises are true. If we have a valid form with a false premise, like All birds can fly; penguin is a bird; therefore penguin can fly, the argument is not sound. The correct concept, then, is a valid argument with all premises true.