A New Theory of Impossibility, Impracticability, and Frustration
本文提出一个经济模型，通过关注合同方的规避投资来解释合同免责原则（不可能、商业不切实际和目的落空）的逻辑和法院判决模式，对理解疫情后合同纠纷有参考价值。
Contract law offers three closely related excuse doctrines: impossibility, commercial impracticability, and frustration of purpose. These doctrines, which allow courts to release parties from their contractual obligations under extreme and unforeseeable circumstances, were central to contract disputes in the aftermath of the COVID-19 pandemic. Yet despite their importance, and despite decades of scholarly attention, these doctrines remain a puzzle, widely considered difficult to explain and justify. Existing economic theory sees contractual excuse doctrines as a risk-allocation mechanism; although highly influential, this standard theory leaves many questions unanswered. We offer a simple economic model explaining contractual excuse doctrines by focusing on avoidance investments, that is, investments by contractual parties designed to escape their obligations and wriggle their way out of their contracts. We show that the proposed model offers a straightforward explanation for contractual excuse doctrines, illustrating their underlying logic and accounting for the key patterns observed in courts’ decisions.