The past is a ghost, haunting the present.

Natural experiments are a powerful tool for understanding causal relationships in the real world.

The ultimate tragedy is not the oppression and cruelty by the bad people but the silence over that by the good people.

I never write Metropolis for seven cents because I can get the same price for city. I never write policeman because I can get the same money for cop.

My attitude is that if you push me towards something that you think is a weakness, then I will turn that perceived weakness into a strength.