Characters in Juno and the Paycock regularly deceive and are regularly deceived.
Both Mary and Johnny are deceived into thinking that sticking to their “principles” will improve their position in life.
Despite needing her job, Mary strikes to support the trade unions. Johnny has been deceived into thinking the sacrifices he made risking his life during the Easter Rising would be worthwhile.
By the end of the play Johnny’s idealism has led to his execution and Mary has been abandoned by her fiancé while pregnant with his child.
Mrs Boyle, however, seems to echo the disillusionment of O’Casey himself as she is more of a realist. She is not convinced by the idea that having principles will automatically improve the lives of her children.
She asks Mary what the local shopkeeper would say if she told him a “principle’s a principle” and informs Johnny that “you lost your best principle, me boy, when you lost your arm”.
Mary is betrayed by Bentham and even Juno incredulously questions how he could "go away t’ England, an’ not to even leave you his address”.
Mrs Boyle herself has been taken in by Bentham. She admits, “I thought he was mad afther you". Because of his class and education both women believed that he was trustworthy and reliable.
Despite the way he has treated Mary, Mrs Boyle remains deceived by Bentham’s class into considering him to be respectable – she refers to him as “a man like Mr. Bentham” even after he has left.
We see Boyle believing that people are real friends, especially after he finds out about his windfall.
Right from the beginning we see him putting his trust in Joxer Daly who ridicules him behind his back when he wonders “who, in the name o’ God, ud leave anythin’ to that oul’ bummer?” Joxer sneers at the family's misfortune, “Sure they were bound to get a dhrop!”
Boyle himself, of course, shows a similar fickle attitude to Joxer whom he is quick to denounce the minute he finds out about his inheritance.
The inheritance changes things for the Boyles and their neighbours.
The family are fooled into thinking Mrs Madigan is a friend, instead she is only interested in profiting from Boyle’s inheritance. She physically assaults him when it is clear she will not be able to do so. Her anger is shown when she asserts “You’re not goin’ to be swankin’ it like a paycock with Maisie Madigan’s money.”
Everyone who befriended the Boyles when there was money to be made from their good fortune rejects them as soon as they find out they have nothing.