Vitalik Buterin: Usually in economics the word “commitment” refers to promises that are *forward-facing*
Indeed, the stress of my argument is on “credible”. Making a commitment/promise is easy, making it credible is hard. One of the common ways to renege on a contract is to falsify, obfuscate, or just reinterpret what was agreed in the contract, and in entering a forward-facing contract it is crucial to credibly signal that one won’t — indeed cannot — engage in such behavior ex post.
This is key to understanding Williamson’s concept of contract: the ex ante, the point of contracting and the ex post. For any suitably complex forward-facing transaction it is impossible at the point of contracting to foresee all future states of the world. So adversarial contracting partners might be tempted to renege on the contract ex post if an unforeseen state makes it attractive to do so. To avoid this, there are commitment devices, whose sole point is to make commitments credible.
So you will always have this forward-facing/backward-facing dichotomy in contracts. What I find so intriguing about crypto is that it offers commitment devices that are built from the viewpoint of the action (the economic transaction), and not from the viewpoint of the actor (the economic agent).
