From time to time (well, OK, quite often!) I write something about the nature of science. One of the things that I think is often misunderstood is that science is not about certainty, it's about knowledge. Because we are constantly adding to our understanding of how the world works, we're never 100% certain about our findings. 99.9%, maybe, but there's always the possibility that new data may make us question that :-) The trouble is that humans seem to want certainty, & if you're craving that certainty, & don't understand why science can't give it to you, then it's easy to deny the science in favour of some other 'way of knowing'.
Anyway, Orac has just written a great post entitled Knowledge versus certainty in skepticism, medicine, & science. It's based on a research paper examining people's reluctance to change particular beliefs when presented with 'belief-challenging' scientific information. I found it a fascinating read :-)