Oh, I do understand.............
As you explain it, the lack of evidence of an event cannot be the proof for the existence of the next event.
In other words, that we have had no further twin towers attacks since 9-11 cannot be used as a proof that any of Bush's acts or machinations cannot be the proof that any Bush method or the Patriot Act has worked to prevent a further attack.
A non event cannot be proved by an overt act. Or, simply this is an admission that deterrence doesn't work.
Don't know the invisible turtle head theory, but I do know the turtle on the fence post theory. We see that one at work on country lanes all through the south.
Whenever you see a turtle on a fence post, somebody put it there.
Publius