 Since voluntariness in contract likely serves several distinct normative functions, its analysis presents a challenge. What powers must an agent exercise over her contractual affairs for her obligations to count as voluntarily undertaken? The law deems agents incapable of contracting if they lack either (1) the ability to understand the nature of a transaction and be responsive to reasons for and against agreeing to it (see R2: §15 and Buckareff and Kasper-Buckareff 2014; on reasons-responsiveness as a general criterion for moral responsibility, see Fischer and Ravizza 1998), or (2) the ability to exercise a degree of control over their choices. Bix (2010) suggests that the common law follows Aristotle in treating an agent’s knowledge and capacity to respond to her reasons, and not just her capacity to act on desires she identifies with, as constitutive of her freedom to contract. In addition to general incapacity, the common law recognizes specific threats to contractual freedom, including lack of material information due to fraud or non-disclosure, intoxication, duress, and, to a lesser extent, cognitive biases when preyed upon within a relationship of trust (R2: §§ 16, 161–163, 173–175). The precise content of these rules is controversial. For instance, there is no legal requirement that parties disclose all relevant information in the generic commercial transaction (F. Miller &amp; Wertheimer 2010), and the line separating permissible from impermissible information asymmetries is deeply contested (Kronman 1978; Craswell 2006).