In social philosophy, a central but controversial ideal. In Aristotle equality of treatment is contingent upon the subjects of the treatment being equal ‘in the relevant respects’. The question of which respects are relevant gives a spectrum ranging from extreme egalitarian approaches, in which virtually nothing forfeits equality of treatment, to élitist ones, in which many things do so. Kantian ethics discerns the equal right of all human beings to treatment as ends in themselves as a foundation of all morality, but the application of this ideal is controversial, since it is unclear what counts as a departure from respect for persons as ends in themselves (persons may clearly be treated sometimes as means, as when someone is quarantined to prevent the spread of an infection, but must not be treated as mere means, or perhaps means in themselves). In political theory the question is whether equalities of social, political, and economic situation are possible, and whether the attempt to create such equalities infringes other values such as liberty, or even undermines too many of the economic and cultural conditions for stable society.