may be too exacting; and in this case, William, refusing the loan, remains as he was before. By the fact of his agreeing to borrow, he proves that he considers it an advantage to himself; he proves, that after every calculation, including the remuneration, whatever it may be, required of him, he still finds it more profitable to borrow than not to borrow. He only determines to do so because he has compared the inconveniences with the advantages. He has calculated that the day on which he returns the plane, accompanied by the remuneration agreed upon, he will have effected more work, with the same labour, thanks to this tool. A profit will remain to him, otherwise he would not have borrowed. The two services of which we are speaking are exchanged according to the law which governs all exchanges, the law of supply and demand. The claims of James have a natural and impassable limit. This is the point in which the remuneration demanded by him would absorb all the advantage which William might find in making use of a plane. In this case, the borrowing would not take place. William would be bound either to make a plane for himself, or to do without one, which would leave him in his original condition. He borrows, because he gains by borrowing. I know very well what will be told me. You will say, William may be deceived, or, perhaps, he may be governed by necessity, and be obliged to submit to a harsh law.
It may be so. As to errors in calculation, they