"He who does not prevent a crime when he can, encourages it."
-- Seneca, Roman philosopher
This quote reminiscent of this Gandhi quote:
“If we could change ourselves, the tendencies in the world would also change. As a man changes his own nature, so does the attitude of the world change towards him. … We need not wait to see what others do.”
Gandhi and Seneca remind us that all of us need to make positive change. It is not enough to know the right thing to do. We all need to act on that knowledge.