This paper is an attempt to elucidate the perplexing definition of justice (ʾadl) that Shahrastānī attributes to the Ashʾarī school in his Kitāb al-milal wal-niḥal: while Muʾtazilites are said to equate justice with wisdom and rational norms, Ashʾarites allegedly identify justice with God’s disposal of his property according to his free will. In Shahrastānī’s account of Ashʾarism, justice is conceived as nothing less than God “freely disposing of his property and his sovereign dominion (mutaṣṣarrif fī milkihi wa-mulkihi).” In fact, it is in virtue of God’s quality as absolute sovereign owner (al-mālik al-muṭlaq) that good and evil are differentiated. Further, for Ashʾarites, it is in virtue of this very quality that a) God is never obliged to exhaust his capacity or his power in his act and to bring all possible being into existence (i.e. he is not bound by an ontological ‘optimum’, what Lovejoy called the “principle of plenitude”) and b) that he is never obliged to act for a reason or a purpose and perform the act that will be most advantageous for creation (i.e. he is not bound by a moral ‘optimum’). The paper will outline a response to the following question: Why do Ashʾarites consider God’s condition as absolute owner of all things to be the source of the differentiation between good and evil, between justice and injustice? Why is property the source of justice rather than its subset? How does this theology of property shape the nature of reality and morality? It will do so by delineating the various theological-philosophical tensions and concepts against which this Ashʾari theology of property emerged— e.g. 1) the Muʾtazilite concept of a purposeful generous God (jawād) who is obliged to reward good deeds, who does nothing in vain and who cannot “keep in reserve” (iddikhār) the best and most beneficial act (al-aṣlaḥ) for human beings; 2) the Neoplatonic concept of purposeless generosity (jūd) understood as the effusion of all possible being by the One who “possesses nothing”; 3) contemporaneous counter-arguments by the least sympathetic opponent of the theory, Qāḍī ʾAbd al-Jabbār.