Catch 22. Sundaram has asked for a clarification on this. Apparently he has come across so many wrong applications of this phrase, he wants to be assured of the correct interpretation and usage. I wish Sundaram had sent a few specimens of the wrong / incorrect usages.
In Joseph Heller’s novel (Catch 22, 1961, the phrase occurs in this novel) pilots flying dangerous missions can seek exemption from duty if they can produce a medical evaluation that they are insane. But if a pilot asks for such an evaluation, he must be sane enough to know his condition. Now the catch is this: If you ask for an evaluation, you are sane and so you cannot claim exemption from flying duties. If you don’t ask, automatically you are taken to be sane and so must fly.
Catch 22 as given in Joseph Heller’s novel is an example of a class of situations where, no matter what you do, you can’t avoid doing the very thing you are trying to avoid. You try to show that there is ground for not doing something. The very act shows that there is ground for you to keep doing what you are trying to avoid.
Another catch 22 situation is described in the well-known Kannada saying: maduve aada horatu hutchu biduvudilla; hutchu bittahoratu maduve aagodilla. Symbolically, If x, then y. But x, only if there is y.
One might wonder whether a catch 22 situation does not present a ‘dilemma’ and in what sense a dilemma differs from a catch 22 situation.
A dilemma as generally understood presents a situation where it is very difficult to decide what to do. As the Longman Dictionary puts it: ‘a situation in which it is very difficult to decide what to do because all the alternatives seem equally good or equally bad. In Logic a dilemma is an argument where proceeding from two premises which seem to exhaust all possibilities, we arrive at two conclusions which are usually, equally unacceptable.
Readers may recall the dilemma which confronted the Keepers of the famous Library of Aexandria in ancient times when the commander of the invading army told them: ‘Either these books are in consonance with what is in the Koran in which case they are superfluous; or they are contrary to what is in the Koran, in which case they are blasphemous. So in either case they deserve to be burnt’. Usually there is a way out of a dilemma of this kind. But there is no way out in a catch 22 situation.
Negative imperatives
Nitin, R has sent the following sentences for comment. 1. Do one thing. 2. Do as I say. 3. Use no cigarettes. 4. Stick no bills. 5. Use no books...6. Do not smoke cigarettes. 7. Do not stick bills. 8. Do not use books.
Do one thing is a famous IE expression, on the lips of every one except very conscious teachers of English. It is a direct translation form the mother tongue. The correct English expression is: Tell you what. But it is doubtful if the correct English expression has any currency at all in the country today. Even those who don’t say ‘Do one thing’ may not say ‘Tell you what’.
As for the other sentences: (4) is preferable to (7); (6) is preferable to (3); (8) with some changes (Don’t use books) is preferable to (5). (2) is Ok.
The interesting ones are the negative sentences. Let’s take a closer look at them.
Generally two structures are available to indicate prohibition: one with Do, another without Do. Don’t litter. No littering. / Don’t smoke. No smoking.
These choices are available where the action prohibited is expressed by a verb, not a verb phrase: to litter, to smoke, to loiter. Where this is not the case the alternatives are not so straightforward. Don’t use books (in an examination). The alternative is not No books.
Use no books sounds quite odd. No books, please is almost an entreaty. In short it is difficult to see what alternative exists.
How then do we explain Stick no bills? If this is Ok, why not Use no books?
By its very nature sticking bills is an act generally viewed with great disfavour. The same cannot be said of using books. Also there is no verb with books expressing prohibition with the same force as stick with bills. Perhaps this explains (?) why stick no bills sounds fine but not Use no books. Perhaps there is a better explanation.
In Joseph Heller’s novel (Catch 22, 1961, the phrase occurs in this novel) pilots flying dangerous missions can seek exemption from duty if they can produce a medical evaluation that they are insane. But if a pilot asks for such an evaluation, he must be sane enough to know his condition. Now the catch is this: If you ask for an evaluation, you are sane and so you cannot claim exemption from flying duties. If you don’t ask, automatically you are taken to be sane and so must fly. 
