But it will be alleged, "Human pursuits are often of a continued tenour, made up of a series of actions, each of which is adopted, not for its own sake, but for the sake of some conclusion in which it terminates. Many of these depend for their success upon co-operation and concert. It is therefore necessary that I should have some clear and specific reason to depend upon the fidelity of my coadjutor, that so I may not be in danger, when I have for a length of time persisted in my exertions, of being frustrated by some change that his sentiments have undergone in the interval." To this it may be replied that such a pledge of fidelity is less frequently necessary than is ordinarily imagined. Were it to be superseded in a variety of cases, men would be taught to have more regard to their own exertions, and less to the assistance of others, which caprice may refuse, or justice oblige them to withhold. They would acquire such merit as should oblige every honest man, if needful, to hasten to their succour; and engage in such pursuits as, not depending upon the momentary caprice of individuals, rested for their success upon the less precarious nature of general circumstances.
Having specified the various limitations that exist as to the utility of promises, it remains for us to discuss their form and obligation in the cases where they may be conceived to be necessary.
Promises are of two kinds, perfect and imperfect. A perfect promise is where the declaration of intention is made by me, for the express purpose of serving as a ground of expectation to my neighbour respecting my future conduct. An imperfect promise is where it actually thus serves as a ground of expectation, though that was not my purpose when I made the declaration.
Imperfect promises are of two classes: I may have reason, or I may have no reason, to know, when I make the declaration, that it will be acted upon by my neighbour, though not assuming the specific form of an engagement.
As to imperfect promises it may be observed that they are wholly unavoidable.