It is, moreover, probable that Ricardo himself did not begin with an elaborate theory of value from which he deduced the laws of distribution, but after having discovered, or having convinced himself that he had discovered, the laws of distribution he attempted to deduce from them a theory of value. One idea had haunted him his whole life long, namely, that with the progress of time nature demanded an ever-increasing application of human toil. No doubt it was this that suggested to him that labour was the foundation, the cause, and the measure of value. But he never came to a final decision on the question, and his statements concerning it are frequently contradictory. We must also confess that his theory of value is far from being his most characteristic work. In the elucidation of that difficult question, vigorous thinker though he was, he has not been much more fortunate than his predecessors. He himself acknowledged this on more than one occasion, and shortly before his death, with a candour that does him honour, he recognised his failure to explain value.[315] 1. THE LAW OF RENT Of all Ricardian theories that of rent is the most celebrated, and it is also the one most inseparably connected with Ricardo’s name. So well known is it that Stuart Mill spoke of it as the economic _pons asinorum_, and it has always been one of the favourite subjects of examiners. The question of rent—that is, of the return which land yields—had occupied the attention of others besides Ricardo. It was the burning question of the day. The problem of rent dominated English political economy during the first half of the nineteenth century, and a later period has witnessed a revival of it in the land nationalisation policy of Henry George. In France there was but a feeble echo of the controversy, for France even long before the Revolution had been a country of small proprietors. Landlordism was far less common there, and where it existed its characteristics were very different. That threefold hierarchy which consisted of a worker toiling for a daily wage in the employ of a capitalist farmer who draws his profits towered over by a landlord in receipt of rents formed a kind of microcosmic picture of the universal process of distribution, but it was seldom as clearly seen in France as it was in England. The first two incomes presented no difficulties. But how are we to explain that other income—that revenue which had created English aristocracy and made English history? The Physiocrats had named it the “net product,” and they argued a liberality of nature and a gift of God. Adam Smith, although withholding the title of creator from nature and bestowing it upon labour, nevertheless admits that a notable portion—perhaps as much as a third of the revenue of land—is due to the collaboration of nature.[316]