Nor is a person who has engaged for another's performing any thing, bound to pay damages and interest for neglect, provided he has done every thing that was necessary on his part towards obtaining its accomplishment. Unless the express terms of the agreement, or the nature of the business require a stricter obligation, positively declaring that, under all circumstances whatever, the thing shall be performed. CHAPTER XII. ON CONTRACTS. Human actions divided into simple or mixed--Gratuitous, or accompanied with mutual obligation--Acts by way of exchange, adjustment of what is to be given or done--Partnership--Contracts--Previous equality--As to knowledge of all circumstances--As to freedom of consent, requisite in contracts of exchange, of sale, of commission and loan--Price of things in what manner to be rated--Transfer of property by sale--What kind contrary to the law of nature--Money--Its use as the standard value of all things--No abatement in the rent or hire of a thing on account of ordinary accidents--Increase or diminution of just salaries--Usury, by what law forbidden--Interest not coming under the name of usury--Insurance--Partnerships of Trade, Naval Associations--Inequality in the terms of a contract no way repugnant to the law of nations. I. and II. Of all human actions, wherein the interest of others is concerned, some are simple, and some are mixed. In those of the former description all service is purely gratuitous, but in the latter it is a traffic of exchange. In the one case the service is granted without a requital, but in the other it is accompanied with an obligation on both sides. Gratuitous services are either immediate in their effect, or to take place at some future time. A beneficial service may be said to be immediately performed, when it confers an advantage, to which the person so benefitted has no direct or absolute right. As a gift transfers property, where there is no previous right. A subject, which has been already discussed. And promises may be said to relate to some future gift, or action, of which a full and sufficient explanation has before been given. Services accompanied with mutual obligation are those where the use of a thing is allowed to any one without a complete alienation, or where labour is given in expectation of some valuable consideration. Under the first of these heads we may reckon the loan and use of all consumable or inconsumable property: and under the latter we may place all commissions to transact business, or all trusts to preserve the property of another. Similar to which are all promises of something to be done, except that they regard a future time. And in this view we may consider all the actions, which are now to be explained.