"Steven Novella, MD: Science does not make statements about proof or disproof. Rather, science is a constantly evolving model or reality that builds upon statements such as — this model of reality makes these predictions, that have either been confirmed or refuted, etc. We say things are probable or likely to be true in science if the predictions that flow from them have been confirmed. We say things are likely to be untrue if they make predictions that turned out to be false. We can further say that certain things are impossible if they create a logical contradiction. If you make a claim, however, that does not make any predictions that can be either confirmed or falsified, then science can say nothing about it. That is agnosticism. That is the difference. It can't say whether or not the "unfalsifiable hypothesis" is true, it cannot make any statements about probability, it cannot say anything — except that it makes no testable predictions. That's it. Anything else is philosophy, ideology, or wishful thinking."