A rule that states that a judge is entitled to decide how to...

A rule that states that a judge is entitled to decide how to interpret a primary rule is a secondary rule; it gives the judge the power to settle disputes by establishing what the correct interpretation of a law is. It is possible, perhaps, to imagine an entire society in which there existed only primary rules. But such a society would be profoundly inept when it comes to resolving controversies about the laws themselves or about their interpretation.

A situation, on the other hand, in which secondary rules would arise in relation to highway-men robbing stagecoaches belongs, at best, to the world of Monty Python. With only one kind of rule in its conceptual armoury, Hart argues, traditional positivism is unable to distinguish between two crucially distinct phenomena: (1) being de facto obliged and (2) having a genuinely normative obligation.

If a gunman puts a gun to your head, you might indeed be, as a matter of empirical fact, obliged to hand over the money. For you to have a normative obligation, in contrast, it is necessary that you accept not only the empirical fact of your being obliged but also the rightness of the system which makes this so (even if you do not accept specific rules in this system).

You accept that to do this or that is your duty ; that it is the right thing to do This notion finds no purchase in the realm of actions performed in response to gunmen’s threats. Hart refers to this dimension of acceptance as the “internal aspect” of obligations, to which he opposes an “external aspect” - the only one that traditional positivism is capable of explaining.

He asks us to imagine someone describing the functioning of a street light in a busy intersection in the following way: when the street light becomes red in the direction of the cars, the likelihood that cars will stop, and that pedestrians will cross the street is very high; when the street light becomes green in the direction of the cars, the likelihood that cars will move forward and pedestrians will stay put increases.

Obviously, Hart points out, such a description fails to mention a fundamental element of what is really going on. The red light is not merely a sign that allows us to predict that drivers and pedestrians will behave in this or that way; rather it is a reason which gives rise to this or that behavior. The red light indicates not simply that I stop, but that I ought to stop. This notion of a reason is not available to traditional legal positivism.