Reasons, in particular practical reasons, are one of the most fundamental normative notions, both in ethics and in law. In the literature on reasons, it has so far been common to consider them as if they are atomic, i.e., as if they have no proper parts. Such an attitude is not necessarily problematic; if one is concerned with the strength or weight of reasons, and their aggregation, one can focus on reasons as “independent” wholes, as it were, perhaps invoking contexts to explain some non-additive phenomena. This “atomitis,” however, meets its natural limits once one is interested in other kinds of issues, such as the subtraction of reasons from one another, or the behavior of partial reasons.