German writers have, for instance, maintained that, alongside of the canonist doctrine with regard to trade, there existed in mediaeval Europe a commercial law, recognised in the secular courts, and altogether opposed to the peculiar doctrines of the canonists.  It is true that parts of mercantile jurisprudence, such as the law of partnership, had to a large extent originated in the social conditions of the time, and would have probably made their appearance even if there had been no canon law or theology.  But though there were branches of commercial law which were, in the main, independent of the canonist doctrine, there were none that were opposed to it.  On the fundamental points of usury and just price, commercial law in the later Middle Ages adopted completely the principles of the canonists.  How entirely these principles were recognised in the practice of the courts which had most to do with commercial suits, viz. those of the towns, is sufficiently shown by the frequent enactments as to usury and as to reasonable price which are found in the town ordinances of the Middle Ages; in England as well as in the rest of Western Europe....  Whatever may have been the effect, direct or indirect, of the canonist doctrine on legislation, it is certain that on its other side, as entering into the moral teaching of the Church through the pulpit and the confessional, its influence was general and persistent, even if it were not always completely successful.’[2] ’Every great change of opinion on the destinies of man,’ says Ingram, ’and the guiding principles of conduct must react in the sphere of material interests; and the Catholic religion had a profound influence on the economic life of the Middle Ages....  The constant presentations to the general mind and conscience of Christian ideas, the dogmatic bases of which were as yet scarcely assailed by scepticism, must have had a powerful effect in moralising life.’[3] According to Dr. Cunningham:  ’The mediaeval doctrine of price was not a theory intended to explain the phenomena of society, but it was laid down as the basis of rules which should control the conduct of society and of individuals.  At the same time current opinion seems to have been so fully formed in accordance with it that a brief enumeration of the doctrine of a just price will serve to set the practice of the day in clearer light.  In regard to other matters, it is difficult to determine how far public opinion was swayed by practical experience, and how far it was really moulded by Christian teaching—­this is the case in regard to usury.  But there can be little doubt about the doctrine of price—­which really underlies a great deal of commercial and gild regulations, and is constantly implied in the early legislation on mercantile affairs.’[4] The same author expresses the same opinion in another work:  ’The Christian doctrine of price, and Christian condemnation of gain at the expense of another man, affected all the mediaeval organisation of municipal