Greenspan argues that dilemmas may be regarded as possible consequences of a set of social rules designed to be simple enough to be teachable. Where these rules prohibit action either way, the problematic motivational force of dilemmas can be explained by reference to the role of emotion as a second-best substitute for action. Since, on the proposed account, emotions underpin the teachings of moral language, Greenspan shows how emotional capacities can affect the very content of morality by providing its motivational force.