But the greatest gap in the Physiocratic doctrine is the total absence of any reference to value, and their grossly material, almost terrestrial, conception of production. They seldom mention value, and what little they do say is often confused and commonplace. Herein lies the source of their mistakes concerning the unproductive character of exchange and industry, which are all the more remarkable in view of the able discussions of this very question by a number of their contemporaries. Among these may be mentioned Cantillon,[112] who resembles them in some respects and whose essay on commerce was published in 1755; the Abbé Galiani, who dealt with the question in his _Della Moneta_ (1750); and the Abbé Morellet, who discussed the same topic in his _Prospectus d’un Nouveau Dictionnaire du Commerce_ (1769). More important than any of them, perhaps, is Condillac, whose work _Du Commerce et du Gouvernement_ was unfortunately not published until 1776; but by that time the Physiocratic system had been completed, and their pre-eminence well established. Turgot, though one of their number, is an exception. He was never a thoroughgoing Physiocrat, and his ideas concerning value are much more scientific.[113] He defines it as “an expression of the varying esteem which man attaches to the different objects of his desire.” This definition gives prominence to the subjective character of value, and the phrases “varying esteem” and “desire” give it greater precision.[114] It is true that he also added that besides this relative attribute value always implied “some real intrinsic quality of the object.” He has frequently been reproached for this, but all that he meant to say was that our desire always implies a certain correctness of judgment, which is indisputable unless every judgment is entirely illusory. But Turgot would never have admitted that. It is possible that Turgot inspired Condillac, and that he himself owed his inspiration to Galiani, whose book, which appeared twenty years earlier, he frequently quotes. This work contains a very acute psychological analysis of value, showing how it depends upon scarcity on the one hand and utility on the other. Besides a difference in his general standpoint, there are other considerations which distinguish Turgot from the members of the Physiocratic school, and it would have been juster to him as well as more correct to have devoted a whole chapter to him.[115] Generally speaking, his views are much more modern and more closely akin to Smith’s. In view of the exigencies of space we must be content to draw attention to the principal doctrines upon which he differs from the Physiocrats. 1. The fundamental opposition between the productivity of agriculture and the sterility of industry, if not altogether abandoned, is at least reduced in importance.