Dr. Cunningham draws attention to the fact that the existence of such a universally received code of economic morality was largely due to the comparative simplicity of the mediaeval social structure, where the relations of persons were all important, in comparison with the modern order, where the exchange of things is the dominant factor.  He further draws attention to the changes which affected the whole constitution of society in the sixteenth and seventeenth centuries, and proceeds:  ’These changes had a very important bearing on all questions of commercial morality; so long as economic dealings were based on a system of personal relationships they all bore an implied moral character.  To supply a bad article was morally wrong, to demand excessive payment for goods or for labour was extortion, and the right or wrong of every transaction was easily understood.’[1] The application of ethics to economic transactions was rendered possible by the existence of one universally recognised code of morality, and the presence of one universally accepted moral teacher.  ’In the thirteenth century, the ecclesiastical organisation gave a unity to the social structure throughout the whole of Western Europe; over the area in which the Pope was recognised as the spiritual and the Emperor as the temporal vicar of God, political and racial differences were relatively unimportant.  For economic purposes it is scarcely necessary to distinguish different countries from one another in the thirteenth century, for there were fewer barriers to social intercourse within the limits of Christendom than there are to-day....  Similar ecclesiastical canons, and similar laws prevailed over large areas, where very different admixtures of civil and barbaric laws were in vogue.  Christendom, though broken into so many fragments politically, was one organised society for all the purposes of economic life, because there was such free intercommunication between its parts.’[2] ‘There were three great threads,’ we read later in the same book, ’which ran through the whole social system of Christendom.  First of all there was a common religious life, with the powerful weapons of spiritual censure and excommunication which it placed in the hands of the clergy, so that they were able to enforce the line of policy which Rome approved.  Then there was the great judicial system of canon law, a common code with similar tribunals for the whole of Western Christendom, dealing not merely with strictly ecclesiastical affairs, but with many matters that we should regard as economic, such as questions of commercial morality, and also with social welfare as affected by the law of marriage and the disposition of property by will....’[3] ‘To the influence of Christianity as a moral doctrine,’ says Dr. Ingram, ’was added that of the Church as an organisation, charged with the application of the doctrine to men’s daily transactions.  Besides the teaching of the sacred books there was a mass of ecclesiastical legislation providing specific prescriptions for the conduct of the faithful.  And this legislation dealt with the economic as well as with other provinces of social activity.’[4]