Tom Robinson displays selflessness against the prevailing vices of the dominant social order through fighting for himself, in a world where colour is held as a prejudice. He stays the honest man, and helps out Madelyn Ewell because nobody else will, and works for her for free because he knows that she needs the help.
"You did all this chopping and work from sheer goodness, boy?"
"Tried to help her, I says."
"You're a mighty good fellow, it seems - did all this for not one penny?"
"Yes suh. I felt right sorry for her, she seemed to try more'n the rest of 'em-" - Tom Robinson (Lee 209)
In the end he sacrificed his life to the aid of her, and yet she went out against him. He didn't have success in surviving, because from the start he wasn't considered an equal person, and only through extreme aid from Atticus were the jury even slightly hesitant about the conviction of him. If he had been a white man, he would have no doubt been proven innocent, however he wasn't and was therefore guilty.
Boo Radley displays selflessness against the prevailing vices of the dominant social order through defending Scout Finch and looking out for the kids regardless of what happens. He watches over everybody from his house, and despite being labelled as 'strange' doesn't leave his house often. In the rare cases that he does, it is to look out for others; for example when he gave a blanket to Scout. Another example is when Boo defends Scout from Bob Ewell (Lee 284). This man succeeds at what he wants, and is allowed to live as he wants - only insulted by those who don't understand him - and thus he is happy.
Atticus Finch embodies this quotation as he strives throughout his life for equality between races, and all aspects of life, and for justice to be served rightfully. He devotes his soul into Tom Robinson's case, and tries as hard as he can for Tom to be freed; despite the racial segregation causing him to have little chance.
“You know the truth, and the truth is this: some Negroes lie, some Negroes are immoral, some Negro men are not to be trusted around women - black or white. But this is a truth that applies to the human race and to no particular race of men. There is not a person in this courtroom who has never told a lie, who has never done an immoral thing, and there is no man living who has never looked upon a woman without desire.” - Atticus ( Lee 217)