“From Smith's principle that labor is the true measure of price—or, as Warren phrased it, that cost is the proper limit of price—these three men [i.e., Josiah Warren, Pierre Proudhon, and Karl Marx] made the following deductions: that the natural wage of labor is its product; that this wage, or product, is the only just source of income (leaving out, of course, gift, inheritance, etc.); that all who derive income from any other source abstract it directly or indirectly from the natural and just wage of labor; that this abstracting process generally takes one of three forms,—interest, rent, and profit; that these three constitute the trinity of usury, and are simply different methods of levying tribute for the use of capital; that, capital being simply stored-up labor which has already received its pay in full, its use ought to be gratuitous, on the principle that labor is the only basis of price; that the lender of capital is entitled to its return intact, and nothing more; that the only reason why the banker, the stockholder, the landlord, the manufacturer, and the merchant are able to exact usury from labor lies in the fact that they are backed by legal privilege.”