catch–22

The original catch-22 was a governmental loophole involved in Joseph Heller’s satirical novel Catch-22. Heller’s novel follows the exploits of a bombardier in World War II, and in doing so shines a light on the relentless and circular bureaucracy of war and wartime governments. The term is introduced to describe the apparent loophole, or catch, that prevents a pilot from asking for a mental evaluation to determine if he’s fit to fly:

There was only one catch and that was Catch-22, which specified that a concern for one's own 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.

Catch-22 appears several times in the novel, always invoked to explain a contradiction or an inescapable paradox caused by the rule itself. It was adopted into general English to refer to an illogical situation, or a problem in which the solution is denied by the problem itself.