Evidence mounts in the strange case of proving that Kevin Bacon, the man who is seven degrees from everyone, has never been to the Liberty Bell in Philadelphia.
The hypothesis: Kevin Bacon has NEVER visited the Liberty Bell
Evidence:
Exhibit A: Kevin Bacon standing in front of a VW beetle – not the Liberty Bell
Exhibits B-E: The Liberty Bell with accompanying visitors, none of which are Kevin Bacon
Exhibit F: The Liberty Bell, yet again, without Kevin Bacon anywhere in sight
Conclusion: Hypothesis accepted – Kevin Bacon has NEVER been to the Liberty Bell
What’s wrong with this argument?
Special thanks to Paul Offit, MD, whose Coursera Vaccines Class inspired this investigation
DownHouseSoftware 
Mehron
October 17, 2013 at 11:40 pm
What if the study relied on 24/7 security camera footage or a visitor logbook as evidence instead? Could one not prove the negative that way?
downhousesoftware
October 18, 2013 at 7:16 am
Proofs are for triangles.
You would certainly strengthen your argument though – especially if the question is modified to ‘Bacon hasn’t visited the liberty bell since …’
There’s a taboo against using the word ‘proof’.
One might argue that this taboo should be loosened when speaking to the public as a means of at least leveling the playing field of discourse. But that solution would lead to its own problems once ‘scientifically proven’ issues get new evidence suggesting they’re wrong.
Mehron
October 18, 2013 at 11:32 am
True. Maybe I could just feel more confident that he hadn’t been there.
“Scientifically proven” seems to a good red flag for spotting questionable claims: The Scientifically Proven Subterfuge
downhousesoftware
October 21, 2013 at 9:17 pm
Bryn replied (via twitter): “Love this: Logic 101. Also, can you imagine a Bayesian solution?” I’m not so handy with stats, so I don’t know how one would do this a la Bayes. I think he would say that his method doesn’t address this question very well, but that the probability was inching towards zero.