When we ask a service of any man, he may either give it us freely, or demand payment for it. Respecting free gift of service, there is no question at present, that being a matter of affection--not of traffic. But if he demand payment for it, and we wish to treat him with absolute equity, it is evident that this equity can only consist in giving time for time, strength for strength, and skill for skill. If a man works an hour for us, and we only promise to work half an hour for him in return, we obtain an unjust advantage. If, on the contrary, we promise to work an hour and a half for him in return, he has an unjust advantage. The justice consists in absolute exchange; or, if there be any respect to the stations of the parties, it will not be in favour of the employer: there is certainly no equitable reason in a man's being poor, that if he give me a pound of bread to-day, I should return him less than a pound of bread to-morrow; or any equitable reason in a man's being uneducated, that if he uses a certain quantity of skill and knowledge in my service, I should use a less quantity of skill and knowledge in his. Perhaps, ultimately, it may appear desirable, or, to say the least, gracious, that I should give in return somewhat more than I received. But at present, we are concerned on the law of justice only, which is that of perfect and accurate exchange;--one circumstance only interfering with the simplicity of this radical idea of just payment--that inasmuch as labour (rightly directed) is fruitful just as seed is, the fruit (or "interest" as it is called) of the labour first given, or "advanced," ought to be taken into account, and balanced by an additional quantity of labour in the subsequent repayment. Supposing the repayment to take place at the end of a year, or of any other given time, this calculation could be approximately made; but as money (that is to say, cash) payment involves no reference to time (it being optional with the person paid to spend what he receives at once or after any number of years), we can only assume, generally, that some slight advantage must in equity be allowed to the person who advances the labour, so that the typical form of bargain will be: If you give me an hour to-day, I will give you an hour and five minutes on demand. If you give me a pound of bread to-day, I will give you seventeen ounces on demand, and so on. All that is necessary for the reader to note is, that the amount returned is at least in equity not to be _less_ than the amount given.