And here it is well enough again to say that we do not question the authority to issue notes or to fit them for a circulating medium, or to promote their circulation by providing for their receipt in payment of debts to the government, and for redemption either in coin or in bonds; in short, to adapt them to use as currency. Nor do we question the lawfulness of contracts stipulating for payment in such notes, or the propriety of enforcing the performance of such contracts by holding the tender of such currency, according to their terms, sufficient. The question is, Has congress power to make the notes of the government, redeemable or irredeemable, a legal tender without contract and against the will of the person to whom they are tendered? In considering this question we assume as a fundamental proposition that it is the duty of every government to establish a standard of value. The necessity of such a standard is indeed universally acknowledged. Without it the transactions of society would become impossible. All measures, whether of extent, or weight, or value, must have certain proportions of that which they are intended to measure. The unit of extent must have certain definite length, the unit of weight certain definite gravity, and the unit of value certain definite value. These units, multiplied or subdivided, supply the standards by which all measures are properly made. The selection, therefore, by the common consent of all nations, of gold and silver as the standard of value was natural, or, more correctly speaking, inevitable. For whatever definitions of value political economists may have given, they all agree that gold and silver have more value in proportion to weight and size, and are less subject to loss by wear or abrasion than any other material capable of easy subdivision and impression, and that their value changes less and by slower degrees, through considerable periods of time, than that of any other substance which could be used for the same purpose. And these are qualities indispensable to the convenient use of the standard required. In the construction of the constitutional grant of power to establish a standard of value, _every presumption_ is, therefore, against that which would authorize the adoption of any other materials than those sanctioned by universal consent. But the terms of the only express grant in the constitution of power to establish such a standard leave little room for presumptions. The power conferred is the power to coin money, and these words must be understood as they were used at the time the constitution was adopted. And we have been referred to no authority which at that time defined coining otherwise than as minting or stamping metals for money; or money otherwise than as metal coined for the purposes of commerce. These are the words of Johnson, whose great dictionary contains no reference to money of paper.