If I predict it's going to rain soon because of a long dry spell, when it rains that doesn't prove me wrong.

Of course not, you have a pattern of weather to base that on, in which dry spells were consistently followed by rain.

Where is the basis for a lack of subversion? Historically, a lack of subversion has meant no subversion was ever planned, on what basis is this different for the 5th Column?

Okay, say it's 6 months. Does that make his argument non-contradictory?

Yes, because now your evidence is that, if there is a 5th column, major subversion occurs every 6 months. This is testable.

His classification of a lack of subversion as evidence that the 5th Column is planning a major strike flies in the face of history - he has a small handful of anomalies to rely on. That's all.

I'll point to Eliezer's example of mammograms in his "Intuitive Explanation of Bayes Theorem" to help describe what I mean, particularly since it's pretty easy to find a very in-depth beysian analysis of this particular problem by Eliezer himself. In the example, 1% of women get breast cancer. 80% of the time a mammogram will test positive if a woman has breast cancer, 20% of the time it will test negative. 10% of the time a mammogram will test positive for someone who doesn't have breast cancer. This works out to a 7.8% likelihood that a woman has cancer if she gets a positive result on a mammogram. Conversely, getting a negative result on a mammogram results in a 0.22% likelihood that a woman has cancer.

In the Warren scenario, the 5th Column planning an attack is like the 1% breast cancer rate, and finding evidence of subversion is the mammogram. Not finding any evidence of subversion is the exact same as getting a negative on a mammogram in the breast cancer scenario. It has happened, sure, but it is extremely rare and in the vast majority of cases no subversion means no planned subversion. The problem is you don't have a history of major subversion without evidence of subversion. Throughout history it has been the exact opposite, therefore a lack of subversion must have a very low probability for preceding a major subversive attack.

Warren's position is like saying he believes there is a high risk of breast cancer because the mammogram came up negative. The only reasonable response to that is WTF? Yes, it's possible that the fifth column is planning something, but you cannot assume that because the evidence says otherwise, that's not reasonable at all. You can come to the conclusion through other evidence, but not with that evidence.

What Warren managed to do is take evidence that did not support his fear and claim that it did. It doesn't make any sense, it is an unreasonable position to take.

Now, if Warren had said "There is a very low likelihood that the 5th Column is planning a surprise attack, but I am not willing to take that risk" then it's an entirely different situation, and that is a completely reasonable response. If breast cancer means being forced to fight through Dante's 9 levels of hell, then it might be worth a double-mastectomy in spite of the 1 in 500 chance that it would happen.

I was wrong when I said that a single case of subversion falsifies his position. Obviously surprise attacks exist, so that was clearly incorrect, and I think it led to a lot of the disagreement in the discussion. I was looking at the problem too narrowly. However the reason surprise attacks are a surprise is because they are very rare, so the fact that nothing has happened must still overwhelmingly support the idea that nothing will happen. In other words, it is overwhelming evidence against an attack, not for it. That's the only reason surprise attacks work at all, because you you have no evidence to suggest they are coming (and that they haven't attacked is not such evidence).

Hopefully I've explained myself adequately now.

My biggest problem with calling a lack of evidence evidence is that it is unnecessary in the first place, which makes it confusing when it comes to discussing it.

Also, I'm not arguing for or against the existence of the fifth column. I think I was unclear about that earlier, and I think we probably got a signal or two crossed. The fifth column was a fact, it existed in Japan, and it is the reason they were afraid of a fifth column in America.

Warren also never argued their existence, only their activity, so I don't see why you have a Q and an R at all. Re-read the statement, he took the 5th column's existence as a given.

What I'm arguing is the idea that a lack of evidence of subversive activity can be strong evidence that a plan similar to Pearl Harbor is being hatched.

To that end, I went ahead and made some calculations.

These are my assumptions, and I feel they are historically reasonable (I didn't cite studies, so I can't exactly call them accurate):

1% of all subversive plots are surprise plots (a-la Pearl Harbor). I call these p(subversion).

Evidence for such plots I call p(evidence).

90% of the time when there is such a plot, there is evidence of it before the fact. I call this p(evidence|subversion).

This is the critical part of Warren's statement - he is essentially assuming the opposite of what I say here, and I assert this is not reasonable given what we know of such plots. There was even evidence of the Pearl Harbor plot before hand. An attack was expected and planned for; it was really only the location (and the lack of a prior declaration) and precise timing that was a surprise militarily. I've frankly never heard of a case of a surprise attack with absolutely no evidence that it would occur, so I believe I am being extremely generous with this number. I would not accept lowering this number much further than this.

Last, I assert that 5% of the time when evidence is found for subversion, no subversion actually occurs. Again, I think this is a reasonable number, and probably too low. I wouldn't have a problem adjusting this number down as low as 1%.

Everything else is calculated based on these three assumptions.

p(subversion) = 1% p(~subversion) = 99%

p(evidence|subversion) = 90% p(~evidence|subversion) = 10% p(evidence|~subversion) = 4.95% p(~evidence|~subversion) = 94.05%

p(evidence) = 5.85% p(~evidence) = 94.15%

p(subversion|evidence) = 15.52% p(~subversion|evidence) = 35.35% p(subversion|~evidence) = 0.11% p(~subversion|~evidence) = 99.89%

So my conclusion on the question of how likely a lack of evidence implies a plot for subversion is drawn from the last two figures. Given my assumptions, which I believe are consistent with history, 99.89% of the time when there is no evidence of a plot for a surprise attack, there is no plot for a suprise attack. This means 0.11% of the time when there is no evidence of a plot, there actually is a plot.

Thus, likelihood of a Pearl Harbor style plot when there is no evidence to that fact is 0.11%.