Gabriel Zucman
presents his proposal for a global minimum tax on billionaires as one that
citizens must debate. They have to weigh the benefits and costs and ultimately
decide whether to adopt it. In this article, we aim to contribute to this
debate by discussing relevant insights from economic ethics and political
philosophy. Our main claim is that the normative case for Zucman’s proposal is
very strong because it is overdetermined: there are multiple reasons that are,
if each is taken individually, sufficient to justify the proposal. Such a
global minimum tax would help address unmet urgent needs, promote social
cohesion and relational equality, contribute to climate fairness and ecological
transitions, and improve the functioning of democracies. It would also bring
the tax system closer in line with the ability-to-pay principle and help reduce
undeserved wealth inequality. All these normative considerations combined show
that citizens have good reasons to adopt the proposal. If anything, these
considerations imply that citizens should, ultimately, aim for an ambitious
variant of the proposal.