Abstract

A contrary-to-duty obligation is an obligation telling us what ought to be the case if something that is wrong is true. For example: ‘If you have done something bad, you should make amends’. Doing something bad is wrong, but if it is true that you did do something bad, it ought to be the case that you make amends. Here are some other examples: ‘If he is guilty, he should confess’, ‘If you have hurt your friend, you should apologise to her’, ‘If she will not keep her promise to him, she ought to call him’, ‘If the books are not returned by the due date, you must pay a fine’. Alternatively, we might say that a contrary-to-duty obligation is a conditional obligation where the condition (in the obligation) is forbidden, or where the condition is fulfilled only if a primary obligation is violated. In the first example, he should not be guilty; but if he is, he should confess. You should not have hurt your friend; but if you have, you should apologise. She should keep her promise to him; but if she will not, she ought to call him. The books ought to be returned by the due date; but if they are not, you must pay a fine. Contrary-to-duty obligations are important in our moral and legal thinking. They turn up in discussions concerning guilt, blame, confession, restoration, reparation, punishment, repentance, retributive justice, compensation, apologies, damage control, and so forth. The rationale of a contrary-to-duty obligation is the fact that most of us do neglect our primary duties from time to time and yet it is reasonable to believe that we should make the best of a bad situation, or at least that it matters what we do when this is the case. We want to find an adequate symbolisation of such obligations in some logical system. However, it has turned out to be difficult to do that. This is shown by the so-called contrary-to-duty (obligation) paradox, sometimes called the contrary-to-duty imperative paradox. The contrary-to-duty paradox arises when we try to formalise certain intuitively consistent sets of ordinary language sentences, sets that include at least one contrary-to-duty obligation sentence, by means of ordinary counterparts available in various monadic deontic logics, such as the so-called Standard Deontic Logic and similar systems. In many of these systems the resulting sets are inconsistent in the sense that it is possible to deduce contradictions from them, or else they violate some other intuitively plausible condition, for example that the members of the sets should be independent of each other. This article discusses this paradox and some solutions that have been suggested in the literature. (Submitted: 2017-10-23; Published in 2022)