Catch-22 contains the following quote:
There was only one catch and that was Catch-22, which specified that a concern for one's safety in the face of dangers that were real and immediate was the process of a rational mind. Orr was crazy and could be grounded. All he had to do was ask; and as soon as he did, he would no longer be crazy and would have to fly more missions. Orr would be crazy to fly more missions and sane if he didn't, but if he was sane he had to fly them. If he flew them he was crazy and didn't have to; but if he didn't want to he was sane and had to. Yossarian was moved very deeply by the absolute simplicity of this clause of Catch-22 and let out a respectful whistle.
"That's some catch, that Catch-22," he observed.
"It's the best there is," Doc Daneeka agreed.
If there was only one catch, why is it "Catch-22"? I had always thought that "Catch-22" was "the catch after Catch 21 and the catch before Catch 23". Or was it that that particular policy (the one on when you could be grounded) only had one catch and that the other catches applied to other policies? Or that Catch-22 was the "summation" of all the other catches in some sense (because Catch-22 means that they have the right to do anything you don't have the power to stop them from doing)?