proposing that the only limitation to what God can make obligatory is the principle of non-contradiction. Robert Adams defended Ockham's view, noting that it is only a logical possibility that God would command what mankind considers to be immoral, not an actuality. Even if God could logically command these actions, he would not because that is not his character. Eleonore Stump and Norman Kretzmann have responded to the Euthyphro dilemma by appealing to the doctrine of divine simplicity, a concept associated with Aquinas and Aristotle which suggests that the substance and attributes of God are identical. They propose that God and goodness are identical and that this is what makes his commands good. American philosopher William Alston responded to the Euthyphro dilemma by considering what it means for God to be morally good. If divine command theory is accepted, it implies that God is good because he obeys his own commands; Alston argued that this is not the case and that God's goodness is distinct from abiding by moral obligations. He suggested that a moral obligation implies that there is some possibility that the agent may not honour their obligation; Alston argued that this possibility does not exist for God, so his morality must be distinct from simply obeying his own commands. Alston contended that God is the supreme standard of morality and acts according to his character, which is necessarily good. There is no more arbitrariness in this view than accepting another moral standard. Omnibenevolence Gottfried Wilhelm Leibniz, and some more recent philosophers, challenged the theory of divine command because it seems to entail that God's goodness consists of his following his own commands. It is argued that, if divine command theory is accepted, God's obligations would be what he commanded himself to do; the concept of God commanding himself is seen as incoherent. Neither could God hold any virtues, as a virtue would be the disposition to follow his own commands – if he cannot logically command himself, then he cannot logically have any virtues. Edward Wierenga counters this by claiming that whatever God chooses to do is good, but that his nature means that his actions would always be praiseworthy. William Wainwright argues that, although God does not act because of his commands, it is still logical to say that God has reasons for his actions. He proposes that God is motivated by what is morally good