But practical reasoning is not in general like that. This is because we need to know where we stand. The constraint is here the same as with a system of law. It would be no good having a system of law that refused to articulate general principles and rules, but insisted on ‘treating each case on its merits’. If it were not predictable in advance what would actually count as the merits then we could not regulate our lives by such a ‘system’. It would be no law at all. Similarly in ethics.
