If wages were exorbitantly high in the seventeenth century, and if this is the reason for the laying to pasture of so much arable, how could farmers afford to cultivate the large amount of fresh land which they were bringing under the plow? Is this accounted for not by any expectation of profit from this land but by the statutory requirement that no arable should be laid to pasture unless an equal amount of grass land were plowed in its stead? Pasture in excess of the legal requirements was plowed up, and persons who did not wish to convert any arable to pasture are found increasing their tilled land by bringing grass land under cultivation. The movement cannot be explained, therefore, merely on the basis of the husbandry statutes. Nor is the law itself to be dismissed without further examination, for in it we find the explicit statement that fresh land could be substituted for that then under cultivation, because common-field land was in many cases exhausted; it was therefore better to allow this to be laid to grass while better land was cultivated in its place.[34] Here then, is the simple explanation of the whole problem. The land which was converted from arable to pasture was worn out; but there was fresh land available for tillage, and some of this was brought under cultivation. No alternative explanation can be worked out on the basis of hypothetical wage or price movements. The historian is indeed at liberty to form his own theories as to the trend of prices in the seventeenth century, for he is unhampered by the existence of known records such as those for the sixteenth century; but it is impossible to construct any theory of prices which will explain why the conversion of arable land to pasture continued at a time when much pasture land was being plowed up. It is necessary to choose a theory of prices which will explain either the extension of tillage or the extension of pasture; both cannot be explained by the same prices. If, as some historians assume, the increase of population or some such factor was causing a comparatively rapid increase in the price of grain in this period, the continued conversion of arable to pasture requires explanation. If, as Miss Leonard supposes, the contrary assumption is true, and the products of arable land could be sold to less advantage than those of pasture, then the cause of the conversion of pasture to arable must be sought.