To prevent the recurrence of evils of this character not only was the clause inserted in the constitution prohibiting the states from issuing bills of credit and making anything but gold and silver a tender in payment of debts, but also the more general prohibition, from passing any law impairing the obligation of contracts. "To restore public confidence completely," says Chief Justice Marshall, "it was necessary not only to prohibit the use of particular means by which it might be effected, but to prohibit the use of any means by which the same mischief might be produced. The convention appears to have intended to establish a great principle, that contracts should be inviolable."

It would require very clear evidence, one would suppose, to induce a belief that with the evils resulting from what Marshall terms the system of lax legislation following the Revolution, deeply impressed on their minds, the framers of the constitution intended to vest in the new government created by them this dangerous and despotic power, which they were unwilling should remain with the states, and thus widen the possible sphere of its exercise.

When the possession of this power has been asserted in argument (for until now it has never been asserted in any decision of this court), it has been in cases where a supposed public benefit resulted from the legislation, or where the interference with the obligation of the contract was very slight. Whenever a clear case of injustice, in the absence of such supposed public good, is stated, the exercise of the power by the government is not only denounced but the existence of the power is denied. No one, indeed, is found bold enough to contend that if A has a contract for one hundred acres of land, or one hundred pounds of fruit, or one hundred yards of cloth, congress can pass a law compelling him to accept one-half of the quantity in satisfaction of the contract. But congress has the same power to establish a standard of weights and measures as it has to establish a standard of value, and can, from time to time, alter such standard. It can declare that the acre shall consist of eighty square rods instead of one hundred and sixty, the pound of eight ounces instead of sixteen, and the foot of six inches instead of twelve, and if it could compel the acceptance of the same number of acres, pounds, or yards, after such alteration, instead of the actual quantity stipulated, then the acceptance of one-half of the quantity originally designated could be directly required without going through the form of altering the standard. No just man could be imposed upon by this use of words in a double sense, where the same names were applied to denote different quantities of the same thing, nor would his condemnation of the wrong committed in such case be withheld, because the attempt was made to conceal it by this jugglery of words.

The power of congress to interfere with contracts for the payment of money is not greater or in any particular different from its power with respect to contracts for lands or goods. The contract is not fulfilled any more in one case than in the other by the delivery of a thing which is not stipulated, because by legislative action it is called by the same name. Words in contracts are to be construed in both cases in the sense in which they were understood by the parties at the time of the contract.

Let us for a moment see where the doctrine of the power asserted will lead. Congress has the undoubted right to give such denominations as it chooses to the coins struck by its authority, and to change them. It can declare that the dime shall hereafter be called a dollar, or, what is the same thing, it may declare that the dollar shall hereafter be composed of the grains of silver which now compose the dime. But would anybody pretend that a contract for dollars, composed as at present, could be satisfied by the delivery of an equal number of dollars of the new issue? I have never met any one who would go to that extent. The answer always has been that would be too flagrantly unjust to be tolerated. Yet enforcing the acceptance of paper promises or paper dollars, if the promises can be so called, in place of gold or silver dollars, is equally enforcing a departure from the terms of the contract, the injustice of the measure depending entirely upon the actual value at the time of the promises in the market. Now reverse the case. Suppose congress should declare that hereafter the eagle should be called a dollar, or that the dollar should be composed of as many grains of gold as the eagle, would anybody for a moment contend that a contract for dollars, composed as now of silver, should be satisfied by dollars composed of gold? I am confident that no judge sitting on this bench, and, indeed, that no judge in Christendom could be found who would sanction the monstrous wrong by decreeing that the debtor could only satisfy his contract in such case by paying ten times the value originally stipulated. The natural sense of right which is implanted in every mind would revolt from such supreme injustice. Yet there cannot be one law for debtors and another law for creditors. If the contract can at one time be changed by congressional legislation for the benefit of the debtor it may at another time be changed for the benefit of the creditor.

For acts of flagrant injustice such as those mentioned there is no authority in any legislative body, even though not restrained by any express constitutional prohibition. For as there are unchangeable principles of right and morality, without which society would be impossible, and men would be but wild beasts preying upon each other, so there are fundamental principles of eternal justice, upon the existence of which all constitutional government is founded, and without which government would be an intolerable and hateful tyranny. There are acts, says Mr. Justice Chase, in Calder v. Bull, which the federal and state legislatures cannot do, without exceeding their authority. Among these he mentions a law which punishes a citizen for an innocent action; a law that destroys or impairs the lawful private contracts of citizens; a law that makes a man a judge in his own cause; and a law that takes the property from A and gives it to B. "It is against all reason and right," says the learned justice, "for a people to intrust a legislature with such powers; and therefore it cannot be presumed that they have done it. The genius, the nature, and the spirit of our state governments amount to a prohibition of such acts of legislation, and the general principles of law and reason forbid them. The legislature may enjoin, permit, forbid, and punish; they may declare new crimes, and establish rules of conduct for all its citizens in future cases; they may command what is right and prohibit what is wrong, but they cannot change innocence into guilt, or punish innocence as a crime, or violate the rights of an antecedent lawful private contract, or the right of private property. To maintain that our federal or state legislatures possess such powers, if they had not been expressly restrained, would, in my opinion, be a political heresy, altogether inadmissible in our free republican governments."

In Ogden v. Saunders, Mr. Justice Thompson, referring to the provisions in the constitution forbidding the states to pass any bill of attainder, ex post facto law, or law impairing the obligation of contracts, says: "Neither provision can strictly be considered as introducing any new principle, but only for greater security and safety to incorporate into this charter provisions admitted by all to be among the first principles of government. No state court would, I presume, sanction and enforce an ex post facto law if no such prohibition was contained in the constitution of the United States; so, neither would retrospective laws, taking away vested rights, be enforced. Such laws are repugnant to those fundamental principles upon which every just system of laws is founded. It is an elementary principle, adopted and sanctioned by the courts of justice in this country and in Great Britain, whenever such laws have come under consideration, and yet retrospective laws are clearly within this prohibition."

In Wilkeson v. Leland, Mr. Justice Story, whilst commenting upon the power of the legislature of Rhode Island under the charter of Charles II. said: "The fundamental maxims of a free government seem to require that the rights of personal liberty and private property should be held sacred. At least no court of justice in this country would be warranted in assuming that the power to violate and disregard them, a power so repugnant to the common principles of justice and civil liberty, lurked under any general grant of legislative authority, or ought to be implied from any general expressions of the will of the people. The people ought not to be presumed to part with rights so vital to their security and well-being without very strong and direct expressions of such an intention."

Similar views to these cited from the opinions of Chase, Thompson, Story, and Marshall, are found scattered through the opinions of the judges who have preceded us on this bench. As against their collective force the remark of Mr. Justice Washington, in the case of Evans v. Eaton, is without significance. That was made at nisi prius in answer to a motion for a nonsuit in an action brought for an infringement of a patent right. The state of Pennsylvania had, in March 1787, which was previous to the adoption of the constitution, given to the plaintiff the exclusive right to make, use, and vend his invention for fourteen years. In January, 1808, the United States issued to him a patent for the invention for fourteen years from that date. It was contended, for the nonsuit, that after the expiration of the plaintiff's privilege granted by the state, the right to his invention became invested in the people of the state, by an implied contract with the government, and, therefore, that congress could not consistently with the constitution grant to the plaintiff an exclusive right to the invention. The court replied that neither the premises upon which the motion was founded, nor the conclusion, could be admitted; that it was not true that the grant of an exclusive privilege to an invention for a limited time implied a binding and irrevocable contract with the people that at the expiration of the period limited the invention should become their property; and that even if the premises were true, there was nothing in the constitution which forbade congress to pass laws violating the obligation of contracts.

The motion did not merit any consideration, as the federal court had no power to grant a nonsuit against the will of the plaintiff in any case. The expression under these circumstances of any reason why the court would not grant the motion, if it possessed the power, was aside the case, and is not, therefore, entitled to any weight whatever as authority. It was true, however, as observed by the court, that no such contract with the public, as stated, was implied, and inasmuch as congress was expressly authorized by the constitution to secure for a limited time to inventors the exclusive right to their discoveries, it had the power in that way to impair the obligation of such a contract, if any had existed. And this is perhaps, all that Mr. Justice Washington meant. It is evident from his language in Ogden v. Saunders, that he repudiated the existence of any general power in congress to destroy or impair vested private rights.