The primary purpose of explicit, expressed interpersonal commitments is to provide some reliability of expectation regarding the actions of free persons whose wills are shakable. It is to allow us some grounds for counting on one another. As Hannah Arendt observed, "The remedy for unpredictability, for the chaotic uncertainty of the future, is contained in the faculty to make and keep promises."*
Commitment as it appears in the human community implies a state of affairs in which there is doubt about our future actions. It implies the possibility of failure to perform acts in the future that are intended, however intensely and firmly, now....
Because our wills are indeed shakable, we need a way to assure others that we will be consistent. Because we know our inconsistencies, we need a way to strengthen ourselves for fulfilling our present intentions in an otherwise uncertain future... By commitment we give ourselves bonds (and give others a power) which will help us to do what we truly want to do, but might otherwise not be able to do, in the future. A remedy for inconsistency and uncertainty, commitment is our wager on the truth of our present insight and the hope of our present love.
from Personal Commitments: Beginning, Keeping, Changing (1986), p. 19.
*page 237, The Human Condition (Chicago: University of Chicago Press, 1958).