What is your dangerous idea?

The history of science is replete with discoveries that were considered socially, morally, or emotionally dangerous in their time; the Copernican and Darwinian revolutions are the most obvious. What is your dangerous idea? An idea you think about (not necessarily one you originated) that is dangerous not because it is assumed to be false, but because it might be true?

We live in a world full of insane people. Sanity is an island battered in an ocean of frothing delusion. The people who believe in science are the minority. The people who believe in bloody fairytales are the overwhelming majority.  - Cenk Uygur

 I was debating with my father over the Thanksgiving weekend and discussion passed through to the existence of god.  I mentioned that I tend to see the problem as one of proof.  Since no one has proven that god exists I assume that it doesn't exist.  His retort (and I'm paraphrasing the exchange) was that not being able to prove the existence of god was the same as proving the existence of god - that you have to go on fiath either way.  I tried to explain to him that the absence of evidence isn't proof of existence, but he was not buying/getting it.  Essentially I felt that he thought I was nuts because he felt that a lack of evidence for and a lack of evidence against were the same thing.  In the end the argument wasn't about the existence of god it was about this logical problem.

Problems that seem to arise for most people when dealing with this logic:
       1) the logic is slightly difficult (e.g. sometimes takes double negatives to explain)
       2) the concept becomes more confusing when you're dealing with something that people acknowledge that they cannot see (e.g. god)

After the fact I tried to come up with an analogy to make it personal for my dad and make it obvious how the logic falls apart.  I developed this, mostly because most of my analogies tend to be about cars anyway:

Some people believe mom (my dad's wife) owns a red car but noone has seen it and mom isn't talking.  There are rumours about it - that it's really fancy and really nice and goes really fast - but when pressed everyone who is asked says they heard the rumour from someone else, or thinks they read about it somewhere.  There is no tangible evidence at all that the red car exists - no photos, no tire marks, no credible eye-witnesses, no hoarded swatches of upolstery, no log of oil changes at speedy lube.  The one piece of ambiguous evidence is a scrap of paper, with handwriting that some people believe is mom's, that reads, "wash the red car."  There are 3 possibilities here:
       1) that the car exists and mom is keeping it a secret (she's a bonafide master of secrets)
       2) that the car exists and she doesn't even know that she owns the car (she might be nuts)
       3) the car does not exist contrary to the rumours
So then the question is, does the car exist?  Until it can be proved, it would be best to assume option (3) that the car does not exist.  Any other conclusion than that would expose some sort of delusion.

That said, I'm not sure that this is well constructed enough to be compelling.  I'm not trying to sway my Dad into believing that god doesn't exist (though if that happens I'm not going to complain) but rather that his logic is poor.

Life is a __________ that needs to be __________.

It makes little sense to try to _________ without first reading _________