Productivity is being able to do things that you were never able to do before.
"We sleep safe in our beds because rough men stand ready in the night to visit violence on those who would do us harm."
A story is only as good as the questions it raises.
No arts; no letters; no society; and which is worst of all, continual fear, and danger of violent death; and the life of man, solitary, poor, nasty, brutish, and short.
依靠别人的家产来养肥自己,依靠别人的天地来称尊。 
Every mental state corresponds to a specific brain state.