catch 22

" 'Sure, that's what I mean,' Doc Daneeka said.'A little grease is what makes this world go round.One hand washes the other.Know what I mean?You scratch my back, I'll scratch yours.'
Yossarian knew what he meant.
'That's not what I meant,' Doc Daneeka said, as Yossarian began scratching his back.'I'm talking about co-operation.Favours.You do a favour for me, I'll do one for you.Get it?'
'Do one for me,' Yossarian requested.
'Not a chance,' Doc Daneeka answered. " - Catch 22