According to a different source, this is the passage that comes with this question:
"One of the principal objections inculcated by the more respectable adversaries to the Constitution, is its supposed violation of the political maxim, that the legislative, executive, and judiciary departments ought to be separate and distinct. In the structure of the federal government, no regard, it is said, seems to have been paid to this essential precaution in favor of liberty. The several departments of power are distributed and blended in such a manner as at once to destroy all symmetry and beauty of form, and to expose some of the essential parts of the edifice to the danger of being crushed by the disproportionate weight of other parts. No political truth is certainly of greater intrinsic value, or is stamped with the authority of more enlightened patrons of liberty, than that on which the objection is founded.
The accumulation of all powers, legislative, executive, and judiciary, in the same hands, whether of one, a few, or many, and whether hereditary, self-appointed, or elective, may justly be pronounced the very definition of tyranny. Were the federal Constitution, therefore, really chargeable with the accumulation of power, or with a mixture of powers, having a dangerous tendency to such an accumulation, no further arguments would be necessary to inspire a universal reprobation of the system. I persuade myself, however, that it will be made apparent to every one, that the charge cannot be supported, and that the maxim on which it relies has been totally misconceived and misapplied."
This passage comes from Federalist No. 47. The constitutional principle that is common in both this excerpt and Federalist No. 51 is that of the separation of powers and the system of checks and balances. Both Federalist No. 47 and Federalist No. 51 argue that such a separation is essential to democracy, and in particular, to the protection of minority rights. Moreover, such a principle is strongly defended in the Constitution. Such defense can be found in articles 1, 2 and 3 of the Constitution. Finally, two examples of how this system operates in the United States is the fact that the Supreme Court can declare a law unconstitutional, and the fact that the executive has veto power over a bill passed by Congress.