Maarten Maartensz:    Philosophical Dictionary | Filosofisch Woordenboek                      

 V - Validity


Validity: In logic: A property of arguments, that claims the argument is good in some sense.

A deductive argument is said to be valid iff the conclusion of the argument is true in each case and every case that the premisses of the argument are true.

This is a very important property, for it means that one can assert the truth of a conclusion of a valid deductive argument as soon as one has established the truth of all the premisses of the argument.

Furthermore, it also means that one can assert the falsity of one or more of the premisses of a valid deductive argument if one has established the falsity of the conclusion. (See: Reductio ad absurdum.)

Note that there is a related stronger notion that should not be confused with validity:

A deductive argument is said to be sound iff the argument is valid and all the premisses are true.

A sound deductive argument for a conclusion is the best support one can offer for a conclusion (though of course there may be more or less elegant, short etc. sound arguments for the same conclusion).


See also: Deduction, Logic



 Original: Aug 23, 2004                                                Last edited: 12 December 2011.   Top