To put it simple, I believe (and could be wrong, so please correct me if I am) that if for example, someones leg that was cut off miraculously grew back i a matter of moments, or that someone came into a party claiming to be Jesus and turned water into wine, that the reaction would not be "Oh wow, God really does exist". Instead, the person that had his leg grow back would be put through a large variety of medical tests, the wine would be tested and the person questioned, and even if no answers were discovered, the reaction would be "Science will discover how this is possible eventually".