The procedural justice of free exchange is important, but is presumes that humans are born with equal talents and in equally enabling environments. This is obviously not true: people can be born to parents with high or low socio-economic status and the talents they are born with, like IQ, are normally distributed.  Suppose you’re born with high talents but to parents with a low socio-economic status. That means your parents do not have enough income to spend on your education: their money is all spent on the basic necessities like food and housing. Since you don’t get the education you need to further develop your talents, you will also likely remain stuck in the same socio-economic class, as will your children, and their children. At the same time, the children of rich parents get more opportunities: even when they’re moderately talented, their parents can invest in maximally developing their talents or even give them a large endowment to live from.  An example of this lack of ‘social mobility’ is the United States, where parental income is an important predictor of a child’s future (Upper Bound, 2010). This is not just a gross and unfair inequality: it is also an infringement upon the liberty of the individual, who, in a free market, is effectively and structurally constrained to develop his or her own talents.