A small body of determined spirits fired by an unquenchable faith in their mission can alter the course of history.

This quote by Mohandas Karamchand Gandhi, the man who helped peacefully free India from British rule, means that if a small number people are passionate about a cause, they can bring about monumental changes to society.  A variant of the quote is "A few determined people who have a strong faith in their mission can change the course of history."