ABSTRACT
We drew attention in our first chapter to the importance of the distinction between normative and descriptive statements, and we have shown in connection with natural law theories how the failure to observe it can lead to confusion. Now words like 'rights', 'duties', 'ought', and 'obligation' belong primarily to normative discourse; they are used, that is, in prescribing conduct according to rules, and have a descriptive force only if we assume the rule to be in force, i.e. widely observed, when to know what the rules require of people is to know also what they are likely to do. But in any case to use words like these is to imply a rule of some sort from which the particular prescription derives. 'X has a right to R' is thus a sentence of a quite different type from 'X has a pen'. The latter can be verified by observation of facts; the former must be established by reference to rules.
