Quote: If all the explanations are highly unlikely, am I obliged, nonetheless, to pick and endorse one of them? I hear a great roar from the Notre Dame stadium; either the Irish have scored a touchdown, or an extra point, or a field goal, or a safety, or completed a long pass, or made a long run from scrimmage, or tackled the opposing runner for a loss, or intercepted a pass. Suppose these eight explanations exhaust the field, and suppose the first is slightly more probable than any of the other seven; its probability, on the evidence is .2. Am I obliged to believe that explanation, just because it is more probable than the rest, and even though its probability is much below .5? Whatever happened to agnosticism, withholding belief?
Plantinga, as usual, forgets that he is talking about science when he judges scientific questions and answers.
Scientific heories are judged according to their explaining power and their probability, not according to probability alone. Explaining power include the Occam's Razor principle: among competing hypothesis, we should select the one that doesn't add unnecessary hypothesis. In Plantinga's example, the possible explanations for the roar have all the same explaining power: they do not add further, unnecessary hypothesis to the setting "football game".
To make his analogy better, Plantinga should have added the explanation "The roar happened because an attractive naked woman ran across the field". This explanation adds an extra hypothesis (the naked woman) to the setting. It is, therefore, perfectly justified to disbelieve this hypothesis unless we already have good reasons to believe that a naked woman was actually at the game.
Religious explanations do the same thing: they add an external hypothesis (the infamous "intelligent creator or designer") without providing any direct evidence for the existence of the designer. They should be rejected unless they provide independent evidence for the designer or creator.
Furthermore, actually there is evidence against a creator or a designer: the usual interpretations of quantum mechanics tell us it's impossible to "plan" the development of the universe.
