Two causes contributed to produce this almost total lack of interest in economic subjects. One was the miserable condition of society, still only partially rescued from the ravages of the barbarians, and half organised, almost without industry and commerce; the other was the absence of all economic tradition. The existence of the _Categories_ and _Hermenia_ of Aristotle ensured that the chain of logical study was not broken; the works of Donatus and Priscian sustained some glimmer of interest in grammatical theory; certain rude notions of physics and astronomy were kept alive by the preservation of such ancient elementary treatises as those of Marcian Capella; but economics had no share in the heritage of the past. Not only had the writings of the ancients, who dealt to some extent with the theory of wealth, been destroyed, but the very traces of their teaching had been long forgotten. A good example of the state of thought in economic matters is furnished by the treatment which money receives in the _Etymologies_ of Isidore of Seville, which was regarded in the early Middle Ages as a reliable encyclopædia. 'Money,' according to Isidore, 'is so called because it warns, _monet_, lest any fraud should enter into its composition or its weight. The piece of money is the coin of gold, silver, or bronze, which is called _nomisma_, because it bears the imprint of the name and likeness of the prince.... The pieces of money _nummi_ have been so called from the King of Rome, Numa, who was the first among the Latins to mark them with the imprint of his image and name.'[1] Is it any wonder that the early Middle Ages were barren of economic doctrines, when this was the best instruction to which they had access? [Footnote 1: _Etymol_. xvi. 17.] In the course of the thirteenth century a great change occurred. The advance of civilisation, the increased organisation of feudalism, the development of industry, and the extension of commerce, largely under the influence of the Crusades, all created a condition of affairs in which economic questions could no longer be overlooked or neglected. At the same time the renewed study of the writings of Aristotle served to throw a flood of new light on the nature of wealth.