Professor Finnis addresses some fascinating questions in subsection two of Chapter XI. Specifically, what is a promise, and why is a promise morally binding? To his credit, Prof Finnis correctly notes that the practice of making promises can take many forms (p. 300): “It need not … be assumed that there is only one ‘promising’ practice in any given community; there can indeed be many, containing the same basic elements in varying forms, some wider, some narrower, some more relaxed, others more stringent.”

So, what are these “same basic elements” that all promises share in common? According to Finnis, a promise has two basic elements: a communication of an intention from A to B, and B’s acceptance of this intention. (Or in Finnis’s own words (pp. 298-299): “Centrally, then, a promise is constituted if and only if (i) A communicates to B his intention to undertake, by that very act of communication …, an obligation to perform a certain action (or to see to it that certain actions are performed), and (ii) B accepts this undertaking in the interests of himself, or of A or of some third party, C.”) But at the same time, Finnis also identifies a serious objection to this definition of a promise, an objection first made by David Hume (pictured below): why should the mere utterance of certain words create a moral obligation? Or as Finnis acknowledges (pp. 299-300, emphasis in original): “there is no obligation-creating magic in uttering a sign signifying the creation of obligation. How, then, do promises bind?”

Prof Finnis then restates David Hume’s reciprocity-based solution to this problem: the reason why promises are morally binding is because of self-interest. According to Hume, it is in one’s self-interest to keep one’s promises because “if I do not perform my obligations to others, others will not perform their obligations to me” (p. 302). Finnis, by contrast, unequivocally rejects Hume’s reciprocity line of reasoning. For Finnis, the real reason why promises are morally binding is because the practice of making (and keeping) promises promotes the common good (p. 303): “if one is to be a person who favours and contributes to the common good, one must go along with the practice of promising.”

Alas, I call bullshit. Why? Because as I explained in a previous post (and as no less an authority as James Madison explains in Federalist #10), there is no such thing as a single or unifying “common good”. Instead, polities will consist of diverse factions and interest groups, and those factions and groups are going to have conflicting purposes and goals. We are thus with Hume and Madison and their public choice disciples like James Buchanan and Gordon Tullock on this one. In any case, even if we could identify such an all-encompassing common good or common purpose of a given group, Finnis fails to consider another theoretical problem: immoral or illegal promises. In other words, we need some way to distinguish good common goods from bad common goods. Since we have made this objection in a previous post, we won’t belabor it here. Instead, we will proceed to subsections three and four of Chapter XI in our next post …