The special taxation of land, or of land values, has been strongly urged by Henry George and his followers since the publication of the remarkable book "Progress and Poverty" in 1879. The doctrine there set forth is that the state should "appropriate land rent by taxation," should "tax land values, irrespective of improvements." It is maintained that "a single tax" of this kind would be quite sufficient for all the purposes of government. The main arguments adduced for this plan may be reduced to three propositions: first, private property in land is essentially unjust, because land is made by nature, not by men; second, the plan would make assessment simple and certain by limiting it to the unimproved land, and making unnecessary the more difficult assessment both of tangible improvements and of intangible personal property; and third, it would work a marvelous reform in social conditions, abolishing poverty and greatly increasing production. It is impossible within our limits of space to discuss this proposal further than to indicate that: (1) It assumes an untenable theory of property.[4] (2) It overlooks the difficulty of distinguishing the value of the land "irrespective of improvements," from that of the land as it actually is, a difficulty especially great in the case of agricultural land.[5] The difficulty is present even in the case of urban land when the improvements of filling, draining, and leveling have become incorporated with the site.[6] (3) The plan ignores the stimulus (motivating force) which private ownership has given and still gives to the maintenance and fuller productive use of land. Nowhere has production thriven where the state was the universal landlord. § 10. #Various reforms in land taxation.# While the single tax plan is defective in principle, its wide discussion has served to direct attention toward the need of reform in the taxation of land. Some proposals looking toward this end are widely favored by opponents as well as by advocates of the single tax. Such are the following: (a) The abandonment of the taxation of mortgages.[7] (b) A more correct assessment, in accordance with the present laws, of lots and lands held for speculative purposes, which in practice are now greatly under-assessed. (c) More adequate special franchise taxation upon corporations for special privileges in the public highways. (d) Exemption, in value equal to the costs, of improvements on land, such as buildings, drains, fences, and fertilizers, for a limited time after they are made, perhaps five years. (e) The separate assessment of urban lands used as mere building sites and of the buildings on them. (f) Taxation of the increase ("increment") of urban land values, periodically or on the occasion of transfer of ownership.