But clear thinking about the boundary conditions is needed also to identify the most dangerous of all possible decisions: the one that might—just might—work if nothing whatever goes wrong. These decisions always seem to make sense. But when one thinks through the specifications they have to satisfy, one always finds that they are essentially incompatible with each other. That such a decision might succeed is not impossible—it is merely grossly improbable. The trouble with miracles is not, after all, that they happen rarely; it is that one cannot rely on them.
