The reasonableness of the agency of the national courts in cases in which the state tribunals cannot be supposed to be impartial, speaks for itself. No man ought certainly to be a judge in his own cause, or in any cause in respect to which he has the least interest or bias. This principle has no inconsiderable weight in designating the federal courts as the proper tribunals for the determination of controversies between different states and their citizens. And it ought to have the same operation in regard to some cases between citizens of the same state. Claims to land under grants of different states, founded upon adverse pretensions of boundary, are of this description. The courts of neither of the granting states could be expected to be unbiased. The laws may have even prejudged the question, and tied the courts down to decisions in favor of the grants of the state to which they belonged. And even where this had not been done, it would be natural that the judges, as men, should feel a strong predilection to the claims of their own government.

Having thus laid down and discussed the principles which ought to regulate the constitution of the federal judiciary, we will proceed to test, by these principles, the particular powers of which, according to the plan of the convention, it is to be composed. It is to comprehend “all cases in law and equity arising under the Constitution, the laws of the United States, and treaties made, or which shall be made, under their authority; to all cases affecting ambassadors, other public ministers, and consuls; to all cases of admiralty and maritime jurisdiction; to controversies to which the United States shall be a party; to controversies between two or more states; between a state and citizens of another state; between citizens of different states; between citizens of the same state claiming lands and grants of different states; and between a state or the citizens thereof and foreign states, citizens, and subjects.” This constitutes the entire mass of the judicial authority of the Union. Let us now review it in detail. It is, then, to extend:

First. To all cases in law and equity, arising under the Constitution and the laws of the United States . This corresponds with the two first classes of causes, which have been enumerated, as proper for the jurisdiction of the United States. It has been asked, what is meant by “cases arising under the Constitution,” in contradiction from those “arising under the laws of the United States”? The difference has been already explained. All the restrictions upon the authority of the state legislatures furnish examples of it. They are not, for instance, to emit paper money; but the interdiction results from the Constitution, and will have no connection with any law of the United States. Should paper money, notwithstanding, be emited, the controversies concerning it would be cases arising under the Constitution and not the laws of the United States, in the ordinary signification of the terms. This may serve as a sample of the whole.

It has also been asked, what need of the word “equity”? What equitable causes can grow out of the Constitution and laws of the United States? There is hardly a subject of litigation between individuals, which may not involve those ingredients of fraud , accident , trust , or hardship