AUSTIN in effect defines 'a law' as 'a general command of a
sovereign addressed to his subjects'. His theory of legal system
is implicit in this definition. To make this clear we shall divide
the definition into three parts, each providing an answer to one
of our three main problems: A law is (1) a general command
(2) issued by some person ( Austin's usual expression is 'set' or
'given') ¹ (3) who is a sovereign (that is, is habitually obeyed
by a certain community and does not render habitual obedience
to anyone).

From the second part of the definition a criterion of identity
and a criterion of membership may be derived:

Austin's criterion of identity: A legal system contains all and
only the laws issued by one person (or body of persons).

Austin's criterion of membership: A given law belongs to the
legal system containing laws issued by the legislator of that law. ²
That is Austin's answer to the problem of identity.

The third part of the definition contains most of the material
from which an existence criterion can be extracted:

Austin's criterion of existence: (1) A legal system exists if the com-
mon legislator of its laws is a sovereign. Therefore: (2) A legal
system exists if it is generally efficacious. The transition from (1)
to (2) is guaranteed by the fact that a person is sovereign only
if he is habitually obeyed, and he is habitually obeyed if, and
only if, his commands are generally obeyed. In Chapter II
(sect. 2) we shall modify the criterion to make it more exact.

The first element of the definition of law is our only clue to
Austin's opinion concerning the structure of a law. He never
tackled the problem directly, but he says enough about the
meaning of the term 'general command' to enable us to recon-
struct a rudimentary doctrine of the structure of laws. It will be
one of our main contentions in this chapter that this doctrine

-5-