Abstract
A contrary‐to‐duty obligation is an obligation that tells us what ought to be the case if something that is wrong or forbidden is true. Alternatively, we might say that a contrary‐to‐duty obligation is a conditional obligation where the condition is fulfilled only if a primary obligation is violated. Consider this example: “If you have hurt her feelings, you should make amends.” Since contrary‐to‐duty obligations play an important role in our moral and legal thinking, we want to find a good analysis of this concept. However, it has turned out to be difficult to formalize various contrary‐to‐duty obligations. This is illustrated by the so‐called contrary‐to‐duty paradox. This paradox is generated when we try to symbolize various scenarios that include at least one contrary‐to‐duty obligation in many formal deontic systems, such as Standard Deontic Logic. Such symbolizations are often inconsistent or entail some other problematic consequences. This entry is a brief introduction to this problem.