The net product was just an illusion. The essence of production is not the creation of matter, but simply the accretion of value. But it is not difficult to appreciate the nature of the illusion if we recall the circumstances, and try to visualise the kind of society with which the Physiocrats were acquainted. One section of the community, consisting solely of nobility and clergy, lived upon the rents which the land yielded. Their luxurious lives would have been impossible if the earth did not yield something over and above the amount consumed by the peasant. It is curious that the Physiocrats, while they regarded the artisans as nothing better than servants who depended for their very existence upon the agriculturists, failed to recognise the equally complete dependence of the worthless proprietor upon his tenants. If there had existed instead a class of business men living in ease and luxury, and drawing their dividends, it is quite possible that the Physiocrats would have concluded that there was a net product in industrial enterprise. So deeply rooted was this idea of nature, or God operating through nature, as the only source of value that we find traces of it even in Adam Smith. Not until we come to Ricardo do we have a definite contradiction of it. With Ricardo, rent, the income derived from land, instead of being regarded as a blessing of nature—the _Alma Parens_—which was bound to grow as the “natural order” extended its sway, is simply looked upon as the inevitable result of the limited extent and growing sterility of the land. No longer is it a free gift of God to men, but a pre-imposed tax which the consumer has to pay the proprietor. No longer is it the net product; henceforth it is known as rent. As to the epithet “sterile,” which was applied to every kind of work other than agriculture, we shall find that it has been superseded, and that the attribute “productive” has been successively applied to every class of work—first to industry, then to commerce, and finally to the liberal professions. Even if it were true that industrial undertakings only yield the equivalent of the value consumed, that is not enough to justify the epithet “sterile,” unless, as Adam Smith wittily remarks, we are by analogy to consider every marriage sterile which does not result in the birth of more than two children. To invoke the distinction between addition and multiplication is useless, because arithmetic teaches us that multiplication is simply an abridged method of adding. It seems very curious that that kind of wealth which appeared to the Physiocrats to be the most legitimate and the most superior kind should be just the one that owed nothing to labour, and which later on, under the name of rent, seems the most difficult to justify. But we must not conclude that the Physiocratic theory of the net product possessed no scientific value.