 Sen (1985) distinguishes two basic strategies for justifying markets: from antecedent rights or liberties on the one hand, or from consequences on the other hand. Arguments about antecedent rights and liberties often go hand in hand, as the rights in question are said to protect the liberties in question. In its paradigmatic form, this argument is based on a right to private property. It gives individuals the right to do whatever they like with their property. This includes the right to enter into exchange relationships with others. Prohibiting such exchanges, or interfering with them in any other way, infringes on these rights and thus, it is said, on a basic form of freedom. The attractiveness of such justifications of markets lies in their a priori character and their intuitive plausibility. But they only work if one can defend the a priori rights or liberties on which they are based. Arguments of this kind are therefore often joined with arguments about the naturalness of property rights as existing prior to the state. It is more plausible to hold that property rights must not be compromised if one holds that they are a priori, than when they are understood as dependent on consent by society and enforcement through the state. The naturalness of property rights has often been defended by connecting them to self-ownership and by basing them on the mixing of one’s labor with material things and thereby appropriating them, along Lockean lines (Locke 1960 [1689]; see also Nozick 1974; for the left-libertarian defense of private property (which combines it with very different positions with regard to equality and the role of the state) see e.g., Vallentyne/Steiner 2000). But this view of property rights has been disputed. Many thinkers point out the crucial role of the state in providing and protecting property rights and the right to free contract (see e.g., Murphy/Nagel 2002). Also, many historians of ideas have pointed out that the idea that liberty consists in the unhindered use of one’s property (what MacGilvray (2011) calls “market freedom”) is not the only way in which freedom can be understood, and has historically been understood (see for example Pettit 2006 for a discussion of markets from the perspective of freedom as non-domination, for a more emphatic endorsement of markets from a neo-republican perspective see Taylor 2013). In fact, the strength of such a priori defenses of markets crucially depends on what “counts” as infringement of freedom: does one only “count” coercive rules by the state, or does one also count the obstacles to pursuing one’s interests that one experiences in a market society, which are often the result of numerous decisions by anonymous individuals (cf. e.g., Cohen 1979; Olsaretti 2004, ch. 4–6; MacGilvray 2011, ch. 5). A strict system of private property rights can lead to situations of extreme inequality in which some members of a society are left to starve, so that it becomes questionable in what sense they can be called free. This presents defenders of markets on a priori grounds with a choice: they either have to bite this bullet and accept extreme inequality and poverty as justified. Or they have to step back from their pure a priori position and admit that consequences can play a role in the consideration of markets. Then, one can admit that markets may have to be supplemented by other institutions, and their justification cannot be unconditional any more (Sen 1985). Nevertheless, rights and liberties can continue to play an important role in pro-market arguments, even while being embedded in a wider framework in which, for example, a certain amount of taxation is also defended (for a recent account, called “free market fairness”, which emphasizes the importance of economic liberties as basic rights but also allows for some restriction for the sake of social justice, see Tomasi 2012).