Strong and valid arguments

A valid argument means “there is no possible way for its premises to be true and its conclusion false” (Epstein). This means the premises state such a fact that you can’t draw a conclusion that would not be true as well. But, however, the premises can be false, therefore the conclusion would be true to the premises but the argument itself would be a bad argument. For example, “no one can physically have kids until they are 18 years of age. So you and your dad have to be at least 18 years apart.” Here, we have a valid argument but it is bad because the premise is false.

A strong argument means “there is some possibility for its premises to be true and its conclusion false, but very unlikely” (Epstein). For example, “You could never see Derek’s abs before. Today, you can see them, so he must have been working out lately.” Here, the argument is strong yet the conclusion could be false. Maybe Derek was sick with mono and didn't eat much recently. Or maybe he started throwing up his meals to lose weight. Unlikely, but you still cannot conclude that Derek has been working out.