There can be no doubt also that the more ancient surveys disclose a difference in point of quantity between free and servile holdings, and this again is a strong argument for the belief that free socage must not be considered merely as an emancipated servile tenancy. Where there has been commutation we must suppose that the labour services cannot have been more valuable than the money rent into which they were changed. The free rent into which labour becomes converted is nothing but the price paid for the services surrendered by the lord. It must have stood higher, if anything, than the real value of the labour exchanged, because the exchange entailed a diminution of power besides the giving up of an economic commodity. No matter that ultimately the quit-rents turned out to the disadvantage of the lord, inasmuch as the buying strength of money grew less and less. This was the result of a very long process, and could not be foreseen at the time when the commutation equivalents were settled. And so we may safely lay down the general rule, that when there is a conspicuous difference between the burdens of assessment of free and unfree tenants, such a difference excludes the idea that one class is only an emancipated portion of the other, and supposes that it was from the first a socially privileged one. The Peterborough Black Book, which, along with the Burton Cartulary, presents the most curious instance of an early survey, describes the services of socmen on the manors of the abbey as those of a clearly privileged tenantry[678]. The interesting point is, that these socmen are even subjected to week-work and not distinguishable from villains so far as concerns the quality of their services. Nevertheless the contrast with the villains appears throughout the Cartulary and is substantiated by a marked difference in point of assessment: a socman has to work one or two days in the week when the villain is made to work three or four. Three main points seem established by the survey of rural work and rents. 1. Notwithstanding many vexatious details, the impositions to which the peasantry had to submit left a considerable margin for their material progress. This system of customary rules was effectively provided against general oppression. 2. The development from food-farms to labour organisation, and lastly to money-rents, was a result not of one-sided pressure on the part of the landlords, but of a series of agreements between lord and tenants. 3. The settlement of the burdens to which peasants were subjected depended to a great extent on distinctions as to the social standing of tenants which had nothing to do with economic facts. CHAPTER IV. THE LORD, HIS SERVANTS AND FREE TENANTS. [Medieval rural system.]