PHIL 120 Lecture Notes - Lecture 4: Soundness
Document Summary
Validity - an argument is valid if and only if it is not possible for the premises to be true and the conclusion false. Soundness - an argument is sound if it is valid and all its premises are true (because a valid argument can have false premises or some false premises) Not necessarily so, when some arguments should be classified as valid but there is no logical link between the conclusion and the premises. Logically necessary (tautology) if it is true regardless of how the world might be. Today is any of the seven days. Logically impossible (contradiction) if it is false regardless of how the world might be. Logically contingent (contingency) if it is neither logically necessary nor logically impossible. Logically impossible - if it is inconsistent with the laws of logic. Bill is in montreal and it is not the case that bill is in montreal.
