The following essay analyzes the arguments made by the principal academic proponent of income taxation, Columbia University economist E. R. A Seligman, after it was found to be unconstitutional in 1894. Seligman thought that the prevalent theory of just taxation, that it should be based on a natural right to one’s person and property, was wrong. The principal American philosophical proponent of this natural rights-based approach to taxation was the late Brown University philosopher and economist, Francis Wayland. The essay analyzes the flaws in Seligman’s contention that there are no natural rights and, therefore, no natural property rights, so that taxation could not be justified by the benefits received for the protection of such rights. Instead, he claimed taxation should rest upon a person’s financial capacity. Since that capacity would be most accurately measured by net worth, we would have expected Seligman to endorse a proportionately assessed net worth tax (which was commonly used by the states in the nineteenth century). Alternatively, he argued for an income tax progressively assessed. This essay argues that since income is only a portion of financial capacity, his argument fails.