unchanged at a higher price than that at which it had been bought, for the sake of gain.[3] [Footnote 1: _Tractatus de Origine, etc., Monetarum_.] [Footnote 2: _Tractatus de Origine, etc., Monetarum_, ad. 2.] [Footnote 3: 'Fit autem mercatio cum non ut emptor ea utatur sed ut earn carius vendat etiam non mutatam suo artificio; illa mercatio dicitur proprie negotiatio' (Biel, _op. cit._, IV. xv. 10.)] The legitimacy of trade in this sense was only gradually admitted. The Fathers of the Church had with one voice condemned trade as being an occupation fraught with danger to the soul. Tertullian argued that there would be no need of trade if there were no desire for gain, and that there would be no desire for gain if man were not avaricious. Therefore avarice was the necessary basis of all trade.[1] St. Jerome thought that one man's gain in trading must always be another's loss; and that, in any event, trade was a dangerous occupation since it offered so many temptations to fraud to the merchant.[2] St. Augustine proclaimed all trade evil because it turns men's minds away from seeking true rest, which is only to be found in God, and this opinion was embodied in the _Corpus Juris Canonici_.[3] This early view that all trade was to be indiscriminately condemned could not in the nature of things survive experience, and a great step forward was taken when Leo the Great pronounced that trade was neither good nor bad in itself, but was rendered good or bad according as it was honestly or dishonestly carried on.[4] [Footnote 1: _De Idol_., xi.] [Footnote 2: Ashley, _op. cit._, vol. i. pt. i. p. 129.] [Footnote 3: See _Corpus Juris Canonici_, Deer. I.D. 88 c. 12.] [Footnote 4: _Epist. ad Rusticum_, c. ix.] The scholastics, in addition to condemning commerce on the authority of the patristic texts, condemned it also on the Aristotelean ground that it was a chrematistic art, and this consideration, as we have seen above, enters into Aquinas's article on the subject.[1] [Footnote 1: Rambaud, _op. cit._, p. 52.] The extension of commercial life which took place about the beginning of the thirteenth century, raised acute controversies about the legitimacy of commerce. Probably nothing did more to broaden the teaching on this subject than the necessity of justifying trade which became more and more insistent after the Crusades.[1] [Footnote 1: On the economic influence of the Crusades the following works may be consulted: Blanqui, _Histoire de l'Economie politique_; Heeren, _Essai sur l'Influence politique et sociale des Croisades_; Scherer, _Histoire du Commerce_; Prutz, _Culturgeschichte der Kreuzzüge_; Pigonneau, _Histoire du Commerce de la France_; List, _Die Lehren der Handelspolitischen Geschichte_.]