Defenders of the TSA — much like defenders of the CIA and other "security" organizations — claim that the TSA surely succeeds in stopping terrorists quite often. Those successes, however, are secret and we can't know about them.

This sort of faith-based trust in government might be convincing for some, but it ought to strike most people capable of critical thinking as nonsensical. The fact remains — if we exclude the hypothetical "secret files of amazing successes" maintained by government agencies — there is no empirical evidence that the TSA prevents terrorism, and even in theory, we can easily point to other factors that are much more important in the prevention of another 9/11.