It is a moral concept.

WHITEHOUSE: President Obama and President Peres of Israel Speak at State Dinner | The White House

In one of the best of these, "Crime and Punishment, " from 1991, he rejected the idea that punishment must always serve utilitarian purposes (rehabilitation, deterrence) and defended, on moral grounds, the concept of retribution.

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And the stock market leapt with joy at the news, and then the chairman of the Federal Reserve said, well, wait a minute, I'm sort of opposed to the concept, it would violate the concept of moral hazard.

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His stamping ground is "the moral, emotional, and political colourings of the concept of human nature in modern life".

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