WE have found it necessary, in order to elucidate features
distinctive of law as a means of social control, to introduce
elements which cannot be constructed out of the ideas of an
order, a threat, obedience, habits, and generality. Too much
that is characteristic of law is distorted by the effort to explain
it in these simple terms. Thus we found it necessary to
distinguish from the idea of a general habit that of a social
rule, and to emphasize the internal aspect of rules manifested
in their use as guiding and critical standards of conduct. We
then distinguished among rules between primary rules of
obligation and secondary rules of recognition, change, and
adjudication. The main theme of this book is that so many of
the distinctive operations of the law, and so many of the ideas
which constitute the framework of legal thought, require for
their elucidation reference to one or both of these two types
of rule, that their union may be justly regarded as the
'essence' oflaw, though they may not always be found together
wherever the word 'law' is correctly used. Our justification
for assigning to the union of primary and secondary rules this
central place is not that they will there do the work of a
dictionary, but that they have great explanatory power.
We must now turn our attention to the claim which, in
the perennial discussion of the 'essence' or the 'nature' or 'the
definition' of law, has been most frequently opposed to the
simple imperative theory which we have found inadequate.
This is the general contention that between law and morality
there is a connection which is in some sense 'necessary', and
that it is this which deserves to be taken as central, in any
attempt to analyse or elucidate the notion of law. Advocates
of this view might not be concerned to dispute our criticisms
of the simple imperative theory. They might even concede
that it was a useful advance;