I surfed across this post on Rober Philen's Blog, 'Anthropology, Culture Theory, and Cultural and Political Commentary' this morning titled: Possible, Plausible, Probable, Proven.

Pretty interesting, if I don't say so myself.

The terms do reflect an ascending order of probability (and a nested one – anything that is plausible is also possible; anything proven is also probable, plausible, and possible), though not in a numerically precise way. They represent a sort of qualitative statistics. When we can realistically indicate precise probabilities, that is obviously a useful thing, but even a rough sense of degree of probability is far more useful than no such sense at all.

Errors in thinking arise whenever we jump up this ascending ladder of probability without evidence, or without sufficient evidence (though admittedly, knowing what counts as sufficient evidence is always tricky business). Just because it’s possible that Bigfoot could be running around the Pacific Northwest or elsewhere doesn’t make it plausible, much less probable or proven.