A simple counter example (hopefully shorter and more clear than the other more in depth criticism by michael sullivan) is the scenario where warren had exactly equal priors for organized fifth column, unorganized fifth column, and no fifth column.
p(organized) = .33
p(unorganized) = .33
p(none) = .33
If he was practically certain that an organized fifth column would wait to make a large attack, and a unorganized fifth column would make small attacks then seeing no small attacks his new probabilities would approximately be:
p(organized) = .5
p(none) = .5
So he would be correct in his statement of concern (assuming an organized fifth column would be very bad), even though the probability of no fifth column was also increased.
A simple counter example (hopefully shorter and more clear than the other more in depth criticism by michael sullivan) is the scenario where warren had exactly equal priors for organized fifth column, unorganized fifth column, and no fifth column.
p(organized) = .33
p(unorganized) = .33
p(none) = .33
If he was practically certain that an organized fifth column would wait to make a large attack, and a unorganized fifth column would make small attacks then seeing no small attacks his new probabilities would approximately be:
p(organized) = .5
p(none) = .5
So he would be correct in his statement of concern (assuming an organized fifth column would be very bad), even though the probability of no fifth column was also increased.