The most solid argument, in their opinion—at least the one that was most frequently used—is that these proprietors are either the men who cleared and drained the land or else their rightful descendants. They have incurred or they are incurring expenditure in clearing the land, enclosing it and building upon it—what the Physiocrats call the _avances foncières_.[50] They never get their revenues through some one else as the manufacturers do, and they are anything but parasites. Their portion is _optimo jure_, in virtue of a right prior and superior even to that of the cultivators, for although the cultivators help to make the product, the proprietors help to make the land. The three social classes of the Physiocratic scheme may be likened to three persons who get their water from the same well. It is drawn from the well by members of the productive class in bucketfuls, which are passed on to the proprietors, but the latter class gives nothing in return for it, for the well is of their making. At a respectable distance comes the sterile class, obliged to buy water in exchange for its labour.[51] The Physiocrats failed to notice the contradiction involved in this. If the revenue which the proprietor draws represents the remuneration for his outlay and the return for his expenditure it is no longer a gift of nature, and the net product vanishes, for, by definition, it represented what was left of the gross product after paying all initial expenses—the excess over cost of production. If we accept this explanation of the facts there is no longer any surplus to dispose of. It is as capitalists pure and simple and not as the representatives of God that proprietors obtain their rents. Must we really believe that although these outlays afford some explanation of the existence of private property they supply no means of measuring or of limiting its extent? Is there no connection between these outlays and the revenues which landed proprietors draw? Or must we distinguish between the two portions of the revenue—the one, indispensable, representing the reimbursement of the original outlay, and in every respect comparable to the revenue of the farmer, and the other, being a true surplus, constituting the net product? How can they justify the appropriation of the latter? There is another argument held in reserve, namely, that based upon social utility. They point out that the cultivation of land would cease and the one source of all wealth would become barren if the pioneer were not allowed to reap the fruits of his labour. The new argument is a contradiction of the old. In the former case land was appropriated because it had been cultivated. In the present case land must be appropriated before it can be cultivated. In the former labour is treated as the efficient cause, in the latter as the final cause of production.