How did John Marshall's opinion in Marbury v. Madison strengthen the power of the US Supreme Court?

That the people have an original right to establish for their future government such principles as, in their opinion, shall most conduce to their own happiness is the basis on which the whole American fabric has been erected. The exercise of this original right is a very great exertion; nor can it nor ought it to be frequently repeated. The principles, therefore, so established are deemed fundamental.

And as the authority from which they proceed, is supreme, and can seldom act, they are designed to be permanent. This original and supreme will organizes the government and assigns to different departments their respective powers. It may either stop here or establish certain limits not to be transcended by those departments.

The Government of the United States is of the latter description. The powers of the Legislature are defined and limited; and that those limits may not be mistaken or forgotten, the Constitution is written. To what purpose are powers limited, and to what purpose is that limitation committed to writing, if these limits may at any time be passed by those intended to be restrained?

The distinction between a government with limited and unlimited powers is abolished if those limits do not confine the persons on whom they are imposed, and if acts prohibited and acts allowed are of equal obligation. It is a proposition too plain to be contested that the Constitution controls any legislative act repugnant to it, or that the Legislature may alter the Constitution by an ordinary act. Between these alternatives there is no middle ground.

The Constitution is either a superior, paramount law, unchangeable by ordinary means, or it is on a level with ordinary legislative acts, and, like other acts, is alterable when the legislature shall please to alter it. If the former part of the alternative be true, then a legislative act contrary to the Constitution is not law; if the latter part be true, then written Constitutions are absurd attempts on the part of the people to limit a power in its own nature illimitable. Certainly all those who have framed written Constitutions contemplate them as forming the fundamental and paramount law of the nation, and consequently the theory of every such government must be that an act of the Legislature repugnant to the Constitution is void.

This theory is essentially attached to a written Constitution, and is consequently to be considered by this Court as one of the fundamental principles of our society. It is not, therefore, to be lost sight of in the further consideration of this subject. If an act of the Legislature repugnant to the Constitution is void, does it, notwithstanding its invalidity, bind the Courts and oblige them to give it effect?

Or, in other words, though it be not law, does it constitute a rule as operative as if it was a law? This would be to overthrow in fact what was established in theory, and would seem, at first view, an absurdity too gross to be insisted on. It shall, however, receive a more attentive consideration.".