Therefore, A benevolent and all-powerful god does not exist. Thus it is impossible for a valid argument to have premises that are all true and a false conclusion. Doug is a man. Therefore, Doug is mortal. In order to be valid, an argument doesn't necessarily have to have true premises.
All geniuses are philosophers.
Portmore is a genius. Therefore, Portmore is a philosopher. In order to be valid, an argument doesn't necessarily have to have a true conclusion. If Portmore has a doctorate, then he is licensed to practice medicine. Portmore does have a doctorate.