Recent tax scholarship has embraced the idea of individual endowment taxation, or taxation of human abilities, as an approach to ideal tax theory. Under endowment taxation, individuals are taxed according to their native abilities to command resources, rather than according to any actual index of goods or expenditures, such as income, consumption, or wealth, that otherwise might be thought relevant to the assignment of tax burdens. This Article argues that endowment taxation is incompatible with political theories that might broadly be described as liberal, to the extent such theories support redistribution. It also argues that limited forms of endowment taxation may be available under liberal theories to the extent such theories operate ...