Now the Right to receive any, or any number, of these future profits is an Estate in land: and as the entirety of these Estates may belong to a number of different persons, we have the whole legal doctrines of Estates in remainder, in fee, in tail, in reversion, etc, with all their complications.

Again although this series of future payments is infinite, a simple Algebraical formula shews that it has a finite limit. When the usual Rate of Interest is 3 per cent., the total Property in land is worth about 33 times its annual profit. Consequently if we buy the existing crop on the ground, only one part is Corporeal, the remaining 32 are Incorporeal.

Now when a purchaser has bought land, it may be said, without any very great metaphor, that it owes him a series of payments for ever: for he bought it merely in the belief of its capacity to produce future profits. Hence we may call this Right to receive the future produce of the land, the Credit of the land: and of course by the notation we have adopted, it is Negative.

Now a merchant, or trader of any sort, carrying on a profitable business, is an Economic Quantity which bears in many respects a strong analogy to land. He may have accumulated a quantity of money, the fruits of his past industry: but over and above his accumulated money, he possesses his abilities, his skill, and experience, his character, his capacity in short, or expectation of earning Profits in the future, as he has already done in the past. Thus the Value of a man as an Economic Quantity, just as the Value of land, consists in the Property in the products of his past industry, together with the Property in the products of his future industry, which of course, are Inverse or Opposite, to each other. And as in the previous case if we choose for the sake of convenience to designate the one, Money, as Positive, we may for the sake of distinction designate the other as Negative.

And there are two ways in which the merchant may trade: he may buy goods by exchanging some of his Property in money, or the fruits of his past industry: or he may buy goods by giving in exchange for them the Right, or Property to demand money at a future time which is to be earned by his industry. This Purchasing Power of buying with a Promise to pay instead of with actual money, is, as we have seen in popular language, termed Credit. And as Wealth is anything which has Purchasing Power, it evidently follows that Money and Credit are equally Wealth.

But as we have already seen that Capital is any Wealth, or Economic Quantity, used for the purpose of Profit, Money and Credit may be equally used as Capital.

But as we have already seen that Money and Credit are Inverse or Opposite to each other, Money may be called Positive Capital, and Credit may be called Negative Capital in strict conformity with the analogy of Natural Philosophy.

17. Now as far as we have gone, we have found the adaptation of the Negative Sign sufficient to explain the classification of Property. No one who has studied the Theory of the Negative Sign as developed by mathematicians within the last century, can fail to see that the designation of Property in the proceeds of the future by the Negative Sign, for the purpose of contra-distinguishing it from Property in the proceeds of the past is strictly analogous to its use in Physical and Mathematical Science. A man's Property in the future earnings of his own industry is as clearly a part of his Property, as his right to reap the produce of his own land. And he may sell and transfer or trade with, and make a Profit by, or make Capital of, the one as well as the other.

But as we have observed this general Purchasing Power, or Credit, of the merchant does not enter into Economics until he actually does make a purchase, or effect an exchange with it; and when he does so considerations of a somewhat complex nature arise: and we must describe the facts in order to see how they are to be classified.

When a trader purchases goods with his Credit, or his Promise to pay, the goods become his absolute Property, just as if he had bought them with money. But exactly at the same instant that the Property in the goods is transferred to him, an Obligation, or Nexum, or Contract is created between the two parties, the buyer and the seller. There is created in the person of the seller, or the Creditor, the Right to demand payment for the goods at the agreed upon time; and also there is created in the person of the buyer or the Debtor, the Duty to pay for them at the fixed time.

This Contract, or Obligation, therefore, contains within itself the Right to demand and the Duty to pay: and as these two are manifestly Inverse or Opposite to each other, if the Right to demand is Positive, the Duty to pay is Negative. For a Duty may manifestly be called a Negative Right, just as a Retarding force may be called a Negative Accelerating force. And here at last we have found the true meaning of the expression used by Mathematicians that Debts are Negative Quantities. Property is a Right, but Debt is a Duty. A Contract, therefore, contains two opposite Quantities, the Right to demand and the Duty to pay: and as these are created simultaneously, can only exist simultaneously, and can only be extinguished simultaneously, they are closely analogous to Polar Forces.

Now the error of Thornton, Cernuschi, Euler, Peacock and many others, consists in this, that they consider the Debt to be an actual specific portion of the Debtor's Money, or Goods, separated from his other property, and pledged to the Creditor. But this is a most important and fundamental error. The Debt as we have shewn already has been clearly pointed out in Roman Law, by Pothier, and many others, is the Personal Duty to pay money: and no doubt the Duty to pay at a future time is created: but it is not a Debt in presenti: it is only a Debt in futuro: it is not a Debt or due until the period fixed for payment has come. And therefore until that period has come, it may be treated as absolutely latent, or non-existent. And even supposing that the Debt is payable on demand like a banker's Notes, it may be treated exactly in the same way, until the Notes are actually presented for payment. But the Right to demand, or the Credit, is the present Right, or Property, of the Creditor, which may be sold and transferred like any other goods and chattels, and therefore it is "Res" "Bonum" "Pecunia" and "Merx" and forms the subject of a colossal commerce. And this Credit or Right can only be extinguished by being revested in the person of the Debtor from whom it originally emanated.