The Rule of Equity, or how the world would be different if equity and justice prevailed.
In medieval England, a person who felt the courts of law issued a judgment that was unfair could appeal to the King. Because he was responsible for the just treatment of his subjects, the King could overrule or modify the courts. He delegated this to the Chancery. There arose a distinction between legal and equitable branches of laws and remedies. Later, these were merged, so that courts today are supposed to apply both law and equity.
But equity and justice have broader connotations than resolution of private disputes. Terms such as social justice, economic justice, and environmental justice seek to describe broader measures of the fairness of society.
Income and wealth inequality is a characteristic of all human societies, except posssibly for some relatively small and primitive social groups. It's an inevitable by-product of human diversity. Some people don't care as much about wealth as others; some have more ability to produce things others want; some work more hours, or get more education, or figure out how to use whatever system they're living under to accumulate more wealth.
President Obama believes "a dangerous and growing inequality and lack of upward mobility" is the "defining challenge of our time." Here is how he explained the situation in December, 2013:
Since he has been President, however, poverty, inequality, and debt have all risen dramatically. There is no reason to believe a continuation of his policies will change that. If anything, his policies continue to increase inequality.