The critical step facing every decision maker is when to stop collecting evidence and proceed with the decision act. This is known as the stopping rule. Over the years, several unconnected explanations have been proposed that suggest nonoptimal approaches can account for some of the observable violations of the optimal stopping rule. The current research proposes a unifying explanation for these violations based on a new stopping rule selection (SRS) theory. The main innovation here is the assumption that a decision maker draws from a large set of different kinds of stopping rules and is not limited to using a single one. The SRS theory hypothesizes that there is a storage area for stopping rules—the so-called decision operative space (DOS)—and a retrieval mechanism that is used to select stopping rules from the DOS. The SRS theory has shown good fit to challenging data published in the relevant literature.