The prohibition of usury has always occupied such a large place in histories of the Middle Ages, and particularly in discussions relating to the attitude of the Church towards economic questions, that it is important that its precise foundation and extent should be carefully studied. The usury prohibition has been the centre of so many bitter controversies, that it has almost become part of the stock-in-trade of the theological mob orators. The attitude of the Church towards usury only takes a slightly less prominent place than its attitude towards Galileo in the utterances of those who are anxious to convict it of error. We have referred to this current controversy, not in order that we might take a part in it, but that, on the contrary, we might avoid it. It is no part of our purpose in our treatment of this subject to discuss whether the usury prohibition was or was not suitable to the conditions of the Middle Ages; whether it did or did not impede industrial enterprise and commercial expansion; or whether it was or was not universally disregarded and evaded in real life. These are inquiries which, though full of interest, would not be in place in a discussion of theory. All we are concerned to do in the following pages is to indicate the grounds on which the prohibition of usury rested, the precise extent of its application, and the conceptions of economic theory which it indicated and involved. [Footnote 1: Brants has a very luminous and interesting section on _Cambium, Op. cit._, p. 214 _et seq_.] We must remark in the first place that the prohibition of usury was in no sense peculiar to the Catholic Church in the Middle Ages, but, on the contrary, was to be found in many other religious and legal systems--for instance, in the writings of the Greek and Roman philosophers, amongst the Jews, and the followers of Mohammed. We shall give a very brief account of the other prohibitions of usury before coming to deal with the scholastic teaching on the subject.