Now, as you will see in a minute, capital cannot be accumulated without some motive. You only accumulate capital by doing without a pleasure which you might have at a certain moment, and putting it off to a future time. You go without the immediate enjoyment of your wealth in order to use it for producing further wealth. That means restraint and sacrifice. But restraint and sacrifice require some motive. Why should a man, or a society, do without a present enjoyment if the sacrifice is not to be productive of future good? What happens is this: A man says: “On my present capital I can produce so much wealth. If I accumulate more capital I shall, in the long run, have a larger income. I will therefore forgo my present pleasure. I will add to my capital and have more income in the future through my present self-restraint.” Or again: “If I don’t _keep up_ my capital by continual saving to replace what is consumed in production I shall gradually get _less_ income.” But here comes in a very important law of Economics called “_The Law of Diminishing Returns_.” After a certain point, capital as it accumulates, does not produce a _corresponding_ amount of extra wealth. It produces _some_ more, but not as much in proportion. For instance, if you till a field thoroughly with the use of so many ploughs and horses and so on, you will get such and such a return. If you add a great deal more capital in the shape of food for more labourers and more tillage till you treat the land as a sort of garden, you produce more wealth from that field; but though you may have doubled your capital you will not have doubled your income. You will only have added to it, say, half as much again. If you were to double your capital again, making four times your original amount, using a lot more food for labourers and a lot more implements, you would again have a larger produce, probably, but perhaps only double your original amount: _Four_ times the original amount of capital, and only _twice_, say, the old income. So the process goes on; and in all forms of the production of wealth this formula applies, and is true: “_The returns of increasing capital, so long as the method of production is not changed, get greater in amount, but less in proportion to the total capital employed._” Men developing a certain section of natural forces get 10 per cent. on a small capital, perhaps 5 per cent. on a larger one; on a still larger one only 2½ per cent., and so on, if they apply that capital to the _same section_ of natural forces and in the _same manner_. Well, this advantage which a man gets by adding to his capital at the expense of present enjoyment can be measured.