An argument is valid if and only if the premises entail the conclusion, that is, if and only if the truth of the conclusion necessarily follows from the truth of the premises. A valid argument is one where it is impossible for all the premises to be true and the conclusion false. If Clinton inhaled, then he deserves to spend the rest of his life in prison. Therefore, Clinton deserves to spend the rest of his life in prison.
Some philosophers are tall.
Doug is a philosopher. Therefore, Doug is tall. Doug is either a genius or a complete idiot. Doug is not a complete idiot. Therefore, Doug is a genius.