land-owner must, that it "don't pay" to spend more than a limited amount per acre on a barley field. But he never looked upon society, as Ricardo was prone to do, as a clock destined to run down by the exhaustion of its stored-up force.[1] If he wanted to use more money to advantage on his patch, he would have tried "Flax, Turnips, Clover grass, Madder, etc.," "so as to advance in value from one to an Hundred," as Hartlib advised.[2] He doubtless believed,[3] just as Hume[4] did, that with social progress a smaller portion of the community would suffice to raise food for the whole. This faith, which has been hitherto abundantly justified by the facts, is, of course, not logically incompatible with that form of the law of diminishing returns which is necessary to explain Ricardian rent.[5] But a man who has such faith is unlikely to hit upon the Ricardian formulation of the law. And Petty did not.
The device which played in Petty's theory of rent the place taken by diminishing returns in Ricardo's is clearly indicated in his calculation of the rent of the counties nearest London. "We would first at hazzard compute the materials for food and covering, which the Shires of Essex, Kent, Surrey, Middlesex and Hertford, next circumjacent to London, did communibus annis produce; and would withal compute the Consumptioners of them living in the said five Shires and London. The which if I found to be more than there were Consumptioners living upon the like scope of other Land, or rather upon so much other Land as bore the like quantity of Provisions, then I say that Provisions must be dearer in the
- ↑ I cannot recall whether this comparison was suggested by Mr. Cannan or by Dr. Patten.
- ↑ Political Arithmetick, 2, 4; Writings, i. 249-251.
- ↑ Ibid., 33; loc. cit., 267.
- ↑ "Essay of Commerce," Philosophical Works (1854), iii. 280.
- ↑ Cf. Commons, Distribution of Wealth, 116-159; Clark in Palgrave's Dictionary, i. 602 a.
