Absence of Evidence / Evidence of Absence

I started this off as a reply to a post in another thread, but it ran on a little and I wanted to see if anybody can pull my thinking on it to pieces.

Rain said:

“Absence of evidence is not evidence of absence.”

I see this sentiment expressed a lot, even amongst sceptics, and I wholeheartedly disagree.

To create an example: There is no evidence that a bulldozer has been recently parked in my garden. There is also no evidence that a bulldozer hasn’t been parked in my garden. So how am I to determine which is true? There’s no evidence either way, so let’s look at what the absence of evidence tells me:

1) The ground is soft yet there are no tread marks;
2) The gate is not wide enough to permit a vehicle and the wall is intact with no evidence of demolition and rebuilding;
3) The only place where a crane could fit to lift a bulldozer into my garden is on the street in front of my house, but nobody has seen or heard a crane;
4) Nobody has seen or heard a helicopter carrying a bulldozer, and there is no evident destruction from a helicopter’s down draft, such as loss of roof tiles;
5) I and my wife look out at the garden whenever we’re in the kitchen or the study, and neither of us has ever seen a bulldozer.

Conclusion? There has not been a bulldozer parked in my garden. Now, this is a good example because at face value it’s an extraordinary thing to ask me to believe – Somebody parked a bulldozer in my garden, but there’s no evidence of it now, and I didn’t notice it when it was there. However, there are real-world mechanisms that could make it possible; it’s just incredibly improbable. Occam’s Razor was designed to trim debates like this down to size very easily – Which is more likely: That there wasn’t a bulldozer, or that somebody sleeping-gassed my whole neighbourhood for however long it took to park, leave, unpark and remove all physical traces of, a bulldozer in my garden?

I said earlier that the prima facie extraordinary nature of this example makes it a good one – Because, when you think about it, it’s a good deal less extraordinary than claiming an omnipotent, omnipresent, omniscient being created the entire universe and that (insert whichever religion) just happens to know everything he/she/it thinks about everything. In fact, insert pretty much any extraordinary claim that relies on faith here. There is no evidence that supports those claims, and that is strong evidence that those claims are false.

So have at it UFers. Is my thinking sound?

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