When such quasi-internal devices are unavailable or weak, a more forceful move is to invoke external constraints. For example, we can make our commitment in public in full self-understanding that our embarrassment over publicly failing the commitment would most likely trump our costs of keeping to it. Then we do not face motivation from the commitment itself but from social constraints that make it in our interest to fulfill the commitment. That is to say, we no longer depend on contriving commitments to be motivators in their own right. Indeed, by making the costs of reneging on our commitment high, we can virtually bring our future action of fulfillment into the present so that we tie our present and future motivations into a single net motivation now for action in the future. In a suggestive term of older contract law, we presentiate that future.

Russell Hardin, Trust and Trustworthiness, loc. 231