Substantially increased wealth inequality across the developed world has prompted many philosophers, economists and legal theorists to support comprehensive taxes on all forms of wealth. Proposals include levying taxes on the basis of total wealth, or alternatively the change in the value of capital holdings measured from year-to-year. This contrasts with most existing policies that tax capital assets at the point they are transferred from one beneficiary to another through sale or gifts. Are these tax reforms likely to meet their aims of greater economic and political equality? We argue that these policies are likely to fail because, following neoclassical economic theory, they are based on a conception of capital as possessing given values in what amounts to a static equilibrium. This mischaracterizes the dynamic and subjective character of market economies and the contested value of real instantiations of capital goods. This makes them very difficult, often impossible, to value apart from at the point of voluntary transfer or profit realization. This means most taxes levied on a mark-to-market basis will be arbitrary and unfair. We propose alternative policies based on an income realization approach to taxation that are more likely to curb excessive wealth holdings. This includes introducing international treaties that prohibit preferential tax treatment for individual companies and specific sectors, and broadening the income tax base to include the imputed rent of personal housing wealth.