The mind can play tricks on us. It is common for us to lose perspective and amplify a small event. We have a natural tendency to try to understand what we sense, so even when we find small insufficient bits of information, our mind tries to catalog it as a familiar thing. If we allow ourselves to consider a bigfoot as something within the realm of the possible, then any unfamiliar smell, sound or shadow may be interprited as a bigfoot encounter. It seems real, but did it really happen? Most of us have probably at times experienced a door knock or telephone ringing only to pick up the receiver or open a door and there is no one there. It most likely happens when we are tired, distracted or waking up, our mind isn't fully focused and we get a false signal. This is why science requires us to produce evidence that can be tested and reproduced by others. Too often we see what we would like to see or expect to see, rather then what is actually there.
Here is a good read on the subject:
http://www.amazon.com/Demon-Haunted...2425106&sr=1-1&keywords=a+demon+haunted+world
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