There is therefore a certain complexity in the structure of
the idea of justice. We may say that it consists of two parts:
a uniform or constant feature, summarized in the precept
'Treat like cases alike' and a shifting or varying criterion used
in determining when, for any given purpose, cases are alike
or different. In this respect justice is like the notions of what
is genuine, or tall, or warm, which contain an implicit reference
to a standard which varies with the classification of the
thing to which they are applied. A tall child may be the same
height as a short man, a warm winter the same temperature
as a cold summer, and a fake diamond may be a genuine
antique. But justice is far more complicated than these notions
because the shifting standard of relevant resemblance
between different cases incorporated in it not only varies with
the type of subject to which it is applied, but may often be
open to challenge even in relation to a single type of subject.