When multiple ceasefire agreements fail in South Sudan and eastern Ukraine, or a humanitarian truce in Yemen collapses within hours, one or more of the parties is said to lack “credible commitment.” Similarly, when the Greek side proposes essentially the same deal that it just called a snap referendum to reject, or when the Eurogroup of eurozone finance ministers, following Germany’s lead, simply ignores the unsustainability of Greece’s debt, the ability to execute any deal must be in doubt.