In the first place, this formula was originally a dictum of the civil law merely, the law of the Roman Empire. It was a legal rather than an ethical maxim. Whatever validity it has in morals must be established on moral grounds, by moral arguments. It cannot forthwith be assumed to be morally sound on the mere authority of legal usage. In the second place, it was for a long time applied only to natural products, to the grain grown in a field, to the offspring of domestic animals. It simply enunciated the policy of the law to defend the owner of the land in his claim to such fruits, as against any outsider who should attempt to set up an adverse title through mere appropriation or possession. Thus far, the formula was evidently in conformity with reason and justice. Later on it was extended, both by lawyers and moralists, to cover commercial "fruits," such as, rent from lands and houses, and interest from loans and investments. Its validity in this field will be examined in connection with the justification of interest. More recently the maxim has received the still wider application which we are now considering. Obviously increases in value are quite a different thing from the concrete fruit of the land, its natural product. A right to the latter does not necessarily and forthwith imply a right to the former. In the third place, the formula in question is not a self evident, fundamental principle. It is merely a summary conclusion drawn from the consideration of the facts and principles of social and industrial life. Consequently its validity as applied to any particular situation will depend on the correctness of these premises, and on the soundness of the process by which it has been deduced. The increment tax is sometimes opposed on the ground that it is new, in fact, revolutionary. In some degree the charge is true, but the conditions which the proposal is intended to meet are likewise of recent origin. The case for this legislation rests mainly on the fact that, for the first time in the world's history, land values everywhere show an unmistakable tendency to advance indefinitely. This means that the landowning minority will be in a position to reap unbought and continuous benefits at the expense of the landless majority. This new fact, with its very important significance for human welfare, may well require a new limitation on the right of property in land.