The notion of sufficiency has recently gained some momentum in separate discourses on distributive justice ('sufficientarianism') and the environment ('eco-sufficiency'). An investigation of their relationship is warranted, as their scope overlaps in areas such as environmental justice and socio-economic policy. This paper argues that the two understandings of sufficiency are incompatible, because eco-sufficiency has adopted an extremely perfectionist view of the good life while sufficientarianism is committed to pluralism. A plausible explanation for this incompatibility relates to the two different meanings of the term sufficiency as a limit (eco-sufficiency) and as a minimum requirement (sufficientarianism).

We investigate the prospects of voluntary ecological sufficiency for environmental and climate policy under the constraints implied by political liberalism. We find that freedom of choice restricts sufficiency to rather wealthy societies and that a sufficiency threshold cannot be derived by referring to the poor. Sufficiency can be in conflict with the demands of social justice, i.e. if the sufficiency threshold is below the social minimum implied by social justice. Benefits from sufficiency are highly related to individual perceptions. Such benefits cannot be expressed in a standard preference framework. Consequently, alternative measures of welfare and inequality are required if sufficiency is a significant phenomenon in society. 'Standard' environmental policies can have a pronounced interaction with voluntary sufficiency, i.e. if 'quantity regulation' is present. Overall, the voluntary notion of sufficiency causes a dilemma as sufficiency is largely a matter of civil society. However, voluntary sufficiency is expected to make important contributions to the preservation of ecological resources if properly balanced with social and environmental policies and framed by public discursive control.

Abstract The indifference objection is one of the most powerful objections to sufficientarianism. Critics argue that sufficientarianism is objectionably indifferent to the distribution of benefits and burdens. This article focuses on the criticism of the latter, particularly the claim that sufficientarianism is indifferent to taxation. Contrary to this allegation, it is argued that sufficientarianism warrants progressive taxation, the reason being that even those who are sufficiently well off face the risk of being pushed below sufficiency. This risk decreases the better off someone is as it is easier for those who are better off to deal with sufficiency-threatening circumstances. It is argued that the risk of insufficiency understood as a function of distance to the threshold justifies progressive taxation. The proposed line of reasoning corresponds to the sufficientarian belief that there should be no redistribution between the rich, as the differences in risk of insufficiency eventually become marginal among those who are very well off. Moreover, the proposed rationale for progressive taxation does not depend on prioritarian or egalitarian reasoning. Rather, it transpires that sufficientarianism is well-suited to justify the progressive redistributive system of the modern welfare state.