John Stuart Mill
Inaugural Address delivered to the University of St Andrews, 1 February 1867
Mill was speaking to students about why education should make people willing to act, not only to watch.
the myth (Edmund Burke): The more famous version, "all that is necessary for the triumph of evil is that good men do nothing", is credited to Burke but has never been found in his writings. Mill's 1867 speech is the closest documented source.
Source: Wikiquote