Why are people inclined to praise or fear the unknown?
In the book "Six Impossible Things Before Breakfast: The Evolutionary Origins of Belief", Wolpert (2007) discusses the evolutionary origins of belief.

Although I haven't read it yet, abc news reviewed the book.


  Wolpert argues that our wide range of beliefs, some of which are
  clearly false, grew out of a uniquely human trait. Alone in the animal
  world, humans understand cause and effect, and that, he says, led
  ultimately to the invention of tools, the rapid rise of sophisticated
  technology, and of course, beliefs. Even the earliest humans
  understood that many events that shaped their lives resulted from
  specific causes. Therefore, there must be a cause behind every event.
  
  ...
  
  We want to believe there is a reason for it all, and that leaves
  us predisposed to believe in some things for which there is little or
  no evidence. If a certain belief makes sense out of an otherwise
  senseless event, then it must be true, right?