GROUND RENT A SOCIAL PRODUCT 25 the appreciation in the value of their land may be fairly reckoned as an offset to the imposition of any new tax upon it. This present exemption, however, is not offered as a reason for additional taxation, but rather as a justification for taking the opportunity to transfer the present load from the head and the tail to the back and shoulders of the horse. As an anti-single-tax professor of political economy happily puts it: β€œThe beauty, to my mind, of a tax upon land values is that in a few years nobody pays it.” XII The Single Tax as an Income Tax An income tax has always been a favourite form of tax, because it has been regarded as well calculated to bear upon β€œ each according to his ability.” The taxa tion of ground rent would surely be the purest possible exemplification and application of the principle of the income tax, because it would fall upon all those in comes which are unearned, which are in their nature perpetual, and which are amply able to bear the whole burden of taxation. Of course, such an income tax should have impartial application. A large un earned income should be taxed at the same rate as a small income of the same nature and derived from the same source. If it is right that corporations or other aggregations of capital should engage in business enterprises for profit upon equal terms with indi viduals, then it is right that an impartial income tax should impose at least the same rate upon the many million dollar incomes of the railroads and the coal operators, and United States steel companies, as upon smaller unearned incomes of one, five, or ten thousand dollars, derived from the same source.