Let’s get clear what makes for a “good” argument. An argument is a series of statements (called premises) leading to a conclusion. A sound argument must meet two conditions:
(1) it is logically valid (i.e., its conclusion follows from the premises by the rules of logic), and
(2) its premises are true.
If an argument is sound, then the truth of the conclusion follows necessarily from the premises. But to be a good argument, it’s not enough that an argument be sound. We also need to have some reason to think that the premises are true. A logically valid argument that has, wholly unbeknownst to us, true premises isn’t a good argument for the conclusion. The premises have to have some degree of justification or warrant for us in order for a sound argument to be a good one. But how much warrant? The premises surely don’t need to be known to be true with certainty (we know almost nothing to be true with certainty!).
Perhaps we should say that for an argument to be a good one the premises need to be probably true in light of the evidence. I think that’s fair, though sometimes probabilities are difficult to quantify. Another way of putting this is that a good argument is a sound argument in which the premises are more plausible in light of the evidence than their opposites. You should compare the premise and its negation and believe whichever one is more plausibly true in light of the evidence. A good argument will be a sound argument whose premises are more plausible than their negations.
William Lane Craig