Methods of Ethics

Henry Sidgwick

Book III

Chapter VI


§9. 1 have laid down that a promise is binding in so far as it is understood on both sides similarly: and such an understanding is ordinarily attained with sufficient clearness, as far as the apprehension of express words or signs is concerned. Still, even here obscurity and misapprehension sometimes occur; and in the case of the tacit understandings with which promises are often complicated, a lack of definite agreement is not improbable. It becomes, therefore, of practical importance to decide the question previously raised: What duty rests on the promiser of satisfying expectations which he did not intend to create? I called this a duty not so much of Good Faith as of Justice, which prescribes the fulfilment of normal expectations. How then shall we determine what these are? The method by which we commonly ascertain them seems to be the following. We form the conception of an average or normal man, and consider what expectations he would form under the circumstances, inferring this from the beliefs and expectations which men generally entertain under similar circumstances. We refer, therefore, to the customary use of language, and customary tacit understandings current among persons in the particular relations in which promiser and promisee stand. Such customary interpretations and understandings are of course not obligatory upon persons entering into an engagement: but they constitute a standard which we think we may presume to be known to all men, and to be accepted by them, except in so for as it is explicitly rejected. If one of the parties to an engagement has deviated from this common standard without giving express notice, we think it right that lie should suffer any loss that may result from the misunderstanding. This criterion then is generally applicable: but if custom is ambiguous or shifting it cannot be applied; and then the just claims of the parties become a problem, the solution of which is very difficult, if not strictly indeterminate.

So far we have supposed that the promiser can choose his own words, and that if the promisee finds them ambiguous be can get them modified, or (what comes to the same thing) explained, by the promiser. But we have now to observe that in the case of promises made to the community, as a condition of obtaining some office or emolument, a certain unalterable form of words has to be used if the promise is made at all. Here the difficulties of moral interpretation are much increased. It may be said, indeed, that the promise ought to be interpreted in the sense in which its terms are understood by the community: and, no doubt, if their usage is quite uniform and unambiguous, this rule of interpretation is sufficiently obvious and simple. But since words are often used in different ways by different members of the same society, and especially with different degrees of strictness and laxity, it often happens that a promise to the community cannot strictly be said to be understood in any one sense: the question therefore arises, whether the promiser is bound to keep it in the sense in which it will be most commonly interpreted, or whether he may select any of its possible meanings. And if the formula is one of some antiquity, it is further questioned, whether it ought to be interpreted in the sense which its words would now generally bear, or in that which they bore when it was drawn up; or, if they were then ambiguous, in the sense which appears to have been attached to them by the government that imposed the promise. On all these points it is difficult to elicit any clear view from Common Sense. And the difficulty is increased by the fact that there are usually strong inducements to make these formal engagements, which cause even tolerably conscientious persons to take them in a strained and unnatural sense. When this has been done continually by many persons, a new general understanding grows up as to the meaning of the engagements: sometimes they come to be regarded as `mere forms', or, if they do not reach this point of degradation, they are at least understood in a sense differing indefinitely from their original one. The question then arises, bow far this process of gradual illegitimate relaxation or perversion can modify the moral obligation of the promise for a thoroughly conscientious person. It seems clear that when the process is complete, we are right in adopting the new understanding so far as Good Faith is concerned, even if it palpably conflicts with the natural meaning of language; although it is always desirable in such cases that the form of the promise should be changed to correspond with the changed substance. But when, as is ordinarily the case, the process is incomplete, since a portion of the community understands the engagement in the original strict sense, the obligation becomes difficult to determine, and the judgments of conscientious persons respecting it become divergent and perplexed.

To sum up the results of the discussion: it appears that a clear consensus can only be claimed for the principle that a promise, express or tacit, is binding, if a number of conditions are fulfilled: viz. if the promiser has a clear belief as to the sense in which it was understood by the promisee, and if the latter is still in a position to grant release from it, but unwilling to do so, if it was not obtained by force or fraud, if it does not conflict with definite prior obligations, if we do not believe that its fulfilment will be harmful to the promisee, or will inflict a disproportionate sacrifice on the promiser, and if circumstances have not materially changed since it was made. If any of these conditions fails, the consensus seems to become evanescent, and the common moral perceptions of thoughtful persons fall into obscurity and disagreement.

[ME, Laws and Promises, §8]
[ME, Veracity, §1]