Why the Basic Structure?
John Rawls famously holds that the basic structure is the ‘primary subject of justice.’ By this, he means that his two principles of justice apply only to a society's major political and social institutions, including chiefly the constitution, the economic and legal systems, and (more contentiously) the family structure. This thesis — call it the basic structure restriction — entails that the celebrated difference principle has a narrower scope than one might have expected. It doesn't apply directly to choices that individuals make within the basic structure. Individuals can live up to the demands of justice simply by obeying whatever rules are set by, and by doing what is necessary to sustain, the basic structure; they needn't attempt to benefit maximally the worst off through their personal choices. Nor does the principle apply to interactions taking place beyond the basic structure, on the international stage. International actors can live up to the demands of justice by observing a comparatively modest ‘duty of assistance’ toward severely destitute societies; they needn't make it their aim to benefit maximally the world's poorest individuals.