[However, there are those who maintain] that courts must close their eyes on the Constitution, and see only the law.... This doctrine would subvert the very foundation of all written constitutions. It would declare that an act which, according to the principles and theory of our government, is entirely void, is yet, in practice, completely obligatory. It would declare that if the legislature shall do what is expressly forbidden, such act, notwithstanding the express prohibition, is in reality effectual. [Moreover,] the peculiar expressions of the Constitution of the United States furnish additional arguments in favor of its rejection. The judicial power of the United States is extended to all cases arising under the Constitution. Could it be the intention of those who gave this power, to say that in using it the Constitution should not be looked into? That a case arising under the Constitution should be decided without examining the instrument under which it arises? This is too extravagant to be maintained. In some cases, then, the Constitution must be looked into by the judges. And if they can open it at all, what part of it are they forbidden to read or to obey? There are many other parts of the Constitution which serve to illustrate this subject.... "No person," says the Constitution, "shall be convicted of treason unless on the testimony of two witnesses to the same overt act, or on confession in open court." Here the language of the Constitution is addressed especially to the courts. It prescribes, directly for them, a rule of evidence not to be departed from. If the legislature should change that rule, and declare one witness, or a confession out of court, sufficient for conviction, must the constitutional principle yield to the legislative act? ... It is also not entirely unworthy of observation, that in declaring what shall be the supreme law of the land, the Constitution itself is first mentioned; and not the laws of the United States generally, but those only which shall be made in pursuance of the Constitution, have that rank. Thus, the particular phraseology of the Constitution of the United States confirms and strengthens the principle, supposed to be essential to all written constitutions, that a law repugnant to the Constitution is void; and that courts, as well as other departments are bound by that instrument. There is not a false step in Marshall's argument. It is, for instance, not contended that the language of the Constitution establishes judicial review but only that it "confirms and strengthens the principle." Granting the finality of judicial decisions and that they may not be validly disturbed by legislative enactment, the argument is logically conclusive, whatever practical difficulties it may ignore.