An important consequence of giving highest priority to the metaphor of Moral Strength is that it rules out any explanations in terms of social forces or social class. If it is always possible to muster the discipline to just say no to drugs or sex and to support yourself in this land of opportunity, then failure to do so is laziness and social class and social forces cannot explain your poverty or your drug habit or your illegitimate children. And if you lack such disciple, then by the metaphor of Moral Strength, you are immoral and deserve any punishment you get.
Mirror neurons are neurons in the brain that fire when another person is observed doing a certain action. The neurons fire in imitation of the action being observed, causing the same muscles to act minutely in the observer as are acting grossly in the person actually performing the action. Research on mirror neurons, since their discovery in 1996,  suggests that they may have a role to play not only in action understanding, but also in emotion sharing empathy . Cognitive neuro-scientist Jean Decety thinks that the ability to recognize and vicariously experience what another individual is undergoing was a key step forward in the evolution of social behavior, and ultimately, morality.  The inability to feel empathy is one of the defining characteristics of psychopathy , and this would appear to lend support to Decety's view.