 As this article will endeavour to show, justice takes on different meanings in different practical contexts, and to understand it fully we have to grapple with this diversity. But it is nevertheless worth asking whether we find a core concept that runs through all these various uses, or whether it is better regarded as a family resemblance idea according to which different combinations of features are expected to appear on each occasion of use. The most plausible candidate for a core definition comes from the Institutes of Justinian, a codification of Roman Law from the sixth century AD, where justice is defined as ‘the constant and perpetual will to render to each his due’. This is of course quite abstract until further specified, but it does throw light upon four important aspects of justice.