What does the phrase "the kindness of strangers" mean?

Question

What does the phrase "the kindness of strangers" mean?

Answer 1

That is from a quote from Tennessee Williams play "The Streetcar Named Desire".  

Vivian Leigh played Blanche DuBois in the movie and her famous line was:  "I've always depended on the kindness of strangers."  She was the perfect helpless female who did nothing to help herself, and depended on "kindness" of others to survive.  So, when she met Marlon Brando, she started leaning on him and flirting like crazy.  Then, she was surprised when he expected more than she was prepared to give.

Answer 2

Here is an example.  Thirty men, all who were strangers to each other and the pregnant woman they attempted to rescue, stopped and lifted up a bus.  The woman was pulled out from under the bus, but died.  The child survived and owes his life to the kindness of (in this case thirty) strangers.

Answer 3

Rent a copy of "A Streetcar Named Desire"; you'lll get the answer plus see a great movie as well.