John Rawls (1921-2002) was an American philosopher, whose writings are considered as some of the most important in 20th century political philosophy.
He is famous for his book "A Theory of Justice", in which he attempted to offer a solution to the problem of distributive justice while supporting both liberty and equality.
A Theory of Justice
Rawls was a secret socialist, arguing that everyone is entitled to a fair opportunity at success. While claiming that liberty can remain, he fails to see how forcing the successful (which he considers mere luck!) to aid those who got crushed by the Invisible hand in their failure is an actual punishment.
Furthermore, his theory that principles must chosen from behind a "Veil of Ignorance" contradicts God's all just and all knowing powers. God cannot be ignorant and still He choose our morals perfectly.
His most notable critic was Robert Nozick, who in "Anarchy, State and Utopia" paid tribute to Rawls' contributions, but defended a libertarian viewpoint, according to which it is unjust to redistribute the earnings of the rich and successful amongst the poorer elements of society without their consent. Often "Anarchy, State and Utopia" is read as a companion to "A Theory of Justice."