 Voluntariness might be important to contracts for a number of reasons. A law of involuntary or forced exchange would risk people’s welfare, not just their autonomy. The parties’ consent better tracks exchange efficiency than a court’s judgment. Apart from welfare concerns, if contractual obligation is grounded in promissory morality (see  §1.1),  then promissory principles constrain the law of contracts, including those that condition an agent’s responsibility on a promise having been made freely (Hurd 1996). The choice condition avoids unfairly holding individuals to duties that they lacked a reasonable opportunity to avoid incurring (cf. Scanlon 1998, Watson 1996).