16.8.06

Absence of evidence

Note: This post was started a few weeks ago, and then consigned to the 'save as draft' graveyard. A conversation at work prompted me to drag it out and finish it.

Doom.

I caught the tail end of a programme on WLJC, the religious network, concerning humans and dinosaurs coexisting.

At first, it was promising. A guest, one Dr Kurt Wise, was talking to the host, one Dwight Nelson. Nelson asked Wise about what evidence existed concerning this idea. Wise was clear - no such evidence exists. He even went as far as to shoot down some of the more famous creationist trophies - supposed evidence of human/dinosaur coexistence which are usually faked or are badly misinterpreted bits of rock - with casual ease.

But then came the change that I should really have known was coming.

This paleontologist, this alleged man of science, then went on to explain that the total lack of evidence is irrelevant because there is 'scriptural evidence' of coexistence. As if that means anything.

But what evidence? The bible never mentions dinosaurs. Ever. Not even once. That big huge frikkin' lizards were stomping around the landscape warrants not a single line in this book that is supposed to account the entire history of the world. And that, it's plain to see, is because dinosaurs were unknown when it was written. Just like science fiction of a hundred-or-so years ago often depicted people walking around on the moon breathing freely. Science just did not know there was no atmosphere up there, just as the writers of the manuscripts that became the bible were unaware of the huge and varied history of the Earth.

Wise's argument was typically theistic.

We know that the dinosaurs existed once. We know that they no longer do. Ergo, they died out. Death didn't exist in the world until humans committed sin. Ergo, dinosaurs and humans must have existed together.

Never mind that there is no actual, real, scientific evidence of such a coexistence, never mind that the very scriptures he is relying on make no mention of such a coexistence.

However, I don't want to waste time debunking this piece of idiotic non-logic. What I wanted to write about connects both of the two points in the paragraph above, that of lack of evidence.

'Absence of evidence is not evidence of absence' is the psuedo-scientific 'rule' which is often quoted, especially when retorting to the charge that the evidence does not support the coexistence assertion.

The problem is that it's true - sort of. The way it was taught to me at school was 'absence of proof is not proof of absence.'

The difference is vastly important. Scientists must be cautious of tossing around the word 'proof' too easily. Proof is something science rarely deals with. Science most often simply works on evidence.

As a good example, consider the solar system. Whilst science has gathered so much evidence that the sun is in the centre and the planets - including the Earth - orbit around it that it would be perverse in the extreme to claim anything else, science has not yet 'proved' this to be true. The orbital model of the solar system is a theory. A theory which is supported by a mountain of extremely persuasive evidence and backed up by every possible observation, but a theory nonetheless.

So, does absence of evidence ever mean anything?

Yes. Oh yes. Often, absence of evidence can be every bit as meaningful as the presence of evidence, especially when one can reasonably expect to find such.

For example, as above, The Bible is supposed to be an accounting of the entire history of the world. We know dinosaurs existed, so if both are true, one has a reasonable expectation that these creatures would be mentioned somewhere. Anywhere. Big lizards. Big honking lizards. Big honking lizards, some of which would view humans as a tasty snack. Big honking lizards eating people and crushing things every time they sit down. Oh yeah, we can be reasonably sure that any real eyewitness account of the history of the planet would mention a few of those.

Or the event that - theory has it - wiped them out. We have proof that, many thousands of years ago, this planet often got hit by Very Large Rocks From Space. Some of these VLRFSs were so huge that the dust and ash the impact threw up blotted out the sun for months.

And the bible does not mention these.

On a more scientific note, absence of evidence is meaningful in many ways. When using an ammeter to measure electric current, a measurement of 0 amps is taken to mean 'no current is flowing'. Nobody in their right mind would declare 'there may or may not be a current which we cannot detect for some reason (possibly through Intelligent Electron Moving) so we cannot say for certain that there is no current.'

No, there's no current. Get over it.

There is a complete lack of evidence for a trillion-ton bar of chocolate orbiting Saturn. Should we assume, just to be on the safe side, that such a chocolate bar exists?



This post is dedicated to the Invisible Pink Unicorn, bless her holy hooves.

1 comment:

Joe Min said...

I live in South Korea.
While I was searching something on the web concerning the phrase "Absence of evidence is not evidence of absence.", I found your blog and read your posting, "Absence of evidence".
It was very interesting to me and much more logically true than theist's insistence, in the limit of my knowledge reach. I want to post your writing on my blog in both English and Korean, if you allow anybody to.