individual enterprise, or to discourage those who were inclined to launch commercial undertakings, any more than the insistence on the need for a similar motive in labourers was productive of idleness. What the mediæval teaching on commerce really amounted to was that, while commerce was as legitimate as any other occupation, owing to the numerous temptations to avarice and dishonesty which it involved, it must be carefully scrutinised and kept within due bounds. It was more difficult to insure the observance of the just price in the case of a sale by a merchant than in one by an artificer; and the power which the merchant possessed of raising the price of the necessaries of life on the poor by engrossing and speculation rendered him a person whose operations should be carefully controlled. [Footnote 1: Cunningham, _Growth of English Industry and Commerce_, vol. i. p. 255.] [Footnote 2: P. 255.] [Footnote 3: _Reg. Fus. Tract._, XXXVII. i.] [Footnote 4: Quoted in Janssen, _op. cit._, vol. ii. p. 9.] Finally, it must be clearly understood that the attempt of some modern writers to base the mediæval justification of commerce on an analysis of all commercial gains as the payment for labour rests on a profound misunderstanding. As we have already pointed out, Aquinas distinctly rules out of consideration in his treatment of commerce the case where the goods have been improved in value by the exertions of the merchant. When the element of labour entered into the transaction the matter was clearly beyond doubt, and the lengthy discussion devoted to the question of commerce by Aquinas and his followers shows that in justifying commercial gains they were justifying a gain resting not on the remuneration for the labour, but on an independent title. § 8. _Cambium_. There was one department of commerce, namely, _cambium_, or money-changing, which, while it did not give any difficulty in theory, involved certain difficulties in practice, owing to the fact that it was liable to be used to disguise usurious transactions. Although _cambium_ was, strictly speaking, a special branch of commerce, it was nevertheless usually treated in the works on usury, the reason being that many apparent contracts of _cambium_ were in fact veiled loans, and that it was therefore a matter of importance in discussing usury to explain the tests by which genuine and usurious exchanges could be distinguished. Endemann treats this subject very fully and ably;[1] but for the purpose of the present essay it is not necessary to do more than to state the main conclusions at which he arrives. [Footnote 1: _Studien_, vol. i. p. 75.]