<P> In logic, an argument is valid if and only if it takes a form that makes it impossible for the premises to be true and the conclusion nevertheless to be false . It is not required that a valid argument have premises that are actually true, but to have premises that, if they were true, would guarantee the truth of the argument's conclusion . A formula is valid if and only if it is true under every interpretation, and an argument form (or schema) is valid if and only if every argument of that logical form is valid . </P> <P> An argument is valid if and only if the truth of its premises entails the truth of its conclusion and each step, sub-argument, or logical operation in the argument is valid . Under such conditions it would be self - contradictory to affirm the premises and deny the conclusion . The corresponding conditional of a valid argument is a logical truth and the negation of its corresponding conditional is a contradiction . The conclusion is a logical consequence of its premises . </P>

What is the definition of a valid argument
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