If an array of goods is for sale on a market, one's wealth, the tradable resources one owns, determines what one can purchase from this array. One's income is the increment in wealth one acquires over a given period of time. In any society, we observe some people having more wealth and income, and some having less. At any given time, some societies have a greater average wealth than others. Across time, we can observe societies becoming richer or poorer and showing more or less equal distributions of wealth among their members. Does it matter from an ethical standpoint whether some people have more income and wealth than others? Does securing a more equal distribution of income and wealth either constitute the achievement of something that is intrinsically morally desirable or serve as a reliable means to the achievement of some intrinsic moral value? If we suppose that justice demands, in many circumstances, the equalization of the income or wealth of persons, what principles of justice generate this demand?