Most contemporary philosophers explain the normativity of promises with one of these two strategies: conventionalists say that promises bind because there is a conventional practice (bearing normative meaning) of making promises and every actor whose utterance meets the requirements of that practice is obligated to do what he or she has said; expectationalists say that promises bind because they raise expectations of fulfillment and (at least in most of the cases) it would be wrong for an actor to disappoint expectations that he or she raised. What I want to examine in this post is whether wagers can be considered to bind in the same way that promises can and for the same reasons too. In order to know that, I will compare wagers and promises and see whether they are sufficiently similar to each other. For the sake of this post, I will consider both strategies successful and will establish that, in defending that some institution is similar to a promise, said similarity can hold either by the conventionalist or the expectationalist conception of promises.
As for wagers, they bear the following intuitive similarity to promises. If I bet with you that, if your team wins the game, I will buy you a beer, that appears to be tantamount to me promising that, if your team wins the game, I will buy you a beer. In this treatment, a wager looks like a case of a conditional promise, a promise whose obligation is conditioned to a hypothetical fact, a promise in the form if–then. (The fact that this kind of wager is usually made with a reciprocity clause, such as “but if mine wins, you buy me a beer”, is not a real problem, because it would just be a case of two promises, each one made by each of the betters and intertwined with each other. For the sake of simplicity, I will consider only the case of unilateral wagers, where the first better is committed to do something for the second one if the condition obtains, but the second better is not committed to do something for the first one if the condition does not obtain.) That intuitive similarity between a wager and a conditional promise is the departing point to our analysis.
There is, however, at least two important differences between a wager and a conditional promise. The first one is that, in a wager, the disbelief of the first better in that the condition will obtain is implicit in the wager proposal itself, while a similar disbelief is not necessary in a conditional promise. Betting that I will buy you a beer if your team wins the game suggests that I have a considerable disbelief that your team will in fact win the game. My utterance implies the prediction that your team will not win the game and, to show how confident I am in my prediction, I am even willing to buy you a beer if the future does not confirm it. On the other hand, by saying something like: “Let’s watch the game together in a bar, I promise you that, if your team wins the game, I will buy a beer”, I do not imply that I don’t believe that your team will win the game, but, on the contrary, I believe that it is at least one of the possibilities and commit myself that, if that happens, I will buy a beer. For making the difference still more evident, you can think of a father that knows that his son will apply for a place in a prestigious university. If the father says: “I promise you that, if you get the place, I will give you a car”, that is a kind of incentive, but if he says: “I bet with you that, if you get the place, I will give you a car”, that is a kind of discouragement, or even an offensive challenge.
The second difference between a wager and a conditional promise is that, in a wager, both betters position themselves in a competition picture, in a win-lose situation. If I bet with you that, if your team wins the game, I will buy you a beer, and it turns out that your team does win the game and I do have to buy you a beer, as said in the wager proposal, then I have suffered a kind of loss and you are even expected to feel free to mock me for that. But the same would be strange for a promise. If I promised you that, if your team won the game, I would buy you a bear and it turned out that your team did win the game and I did have to buy you a beer, it is only the fulfillment of a promise, for your team’s winning the game was something that I had expected to possibly happen and my having to buy you a beer was something that I even wanted to do if your team won (which is kind of a win-win situation). There would be no reason to mock me for that; maybe there is even place to thank me in a way for having made that promise and for having complied with it in the end.