“Democratic and aristocratic states are not in their own nature free. Political liberty is to be found only in moderate governments; and even in these it is not always found. It is there only when there is no abuse of power. But constant experience shows us that every man who has power is inclined to abuse it; he goes until he finds limits. Is it not strange, though true, to say that virtue itself has need of limits?.
To prevent this abuse, it is necessary that, by the arrangement of things, power shall stop power. A government may be so constituted, as no man shall be compelled to do things to which the law does not oblige him, nor forced to abstain from things which the law permits.”

Oliver Cromwell, letter to Walter Dundas, 12 September 1650; this is also a recent misattribution.
Misattributed

Source: White-Jacket (1850), Ch. 67
Context: Nature has not implanted any power in man that was not meant to be exercised at times, though too often our powers have been abused. The privilege, inborn and inalienable, that every man has of dying himself, and inflicting death upon another, was not given to us without a purpose. These are the last resources of an insulted and unendurable existence.

17 U.S. (4 Wheaton) 316, 428
McCulloch v. Maryland (1819)

A Vindication of Natural Society (1756)
Context: I need not excuse myself to your Lordship, nor, I think, to any honest man, for the zeal I have shown in this cause; for it is an honest zeal, and in a good cause. I have defended natural religion against a confederacy of atheists and divines. I now plead for natural society against politicians, and for natural reason against all three. When the world is in a fitter temper than it is at present to hear truth, or when I shall be more indifferent about its temper, my thoughts may become more public. In the mean time, let them repose in my own bosom, and in the bosoms of such men as are fit to be initiated in the sober mysteries of truth and reason. My antagonists have already done as much as I could desire. Parties in religion and politics make sufficient discoveries concerning each other, to give a sober man a proper caution against them all. The monarchic, and aristocratical, and popular partisans have been jointly laying their axes to the root of all government, and have in their turns proved each other absurd and inconvenient. In vain you tell me that artificial government is good, but that I fall out only with the abuse. The thing! the thing itself is the abuse! Observe, my Lord, I pray you, that grand error upon which all artificial legislative power is founded. It was observed that men had ungovernable passions, which made it necessary to guard against the violence they might offer to each other. They appointed governors over them for this reason! But a worse and more perplexing difficulty arises, how to be defended against the governors? Quis custodiet ipsos custodes? In vain they change from a single person to a few. These few have the passions of the one; and they unite to strengthen themselves, and to secure the gratification of their lawless passions at the expense of the general good. In vain do we fly to the many. The case is worse; their passions are less under the government of reason, they are augmented by the contagion, and defended against all attacks by their multitude.

2014, Review of Signals Intelligence Speech (June 2014)
Context: There was a recognition by all who participated in these reviews that the challenges to our privacy do not come from government alone. Corporations of all shapes and sizes track what you buy, store and analyze our data, and use it for commercial purposes; that’s how those targeted ads pop up on your computer and your smartphone periodically. But all of us understand that the standards for government surveillance must be higher. Given the unique power of the state, it is not enough for leaders to say: Trust us, we won’t abuse the data we collect. For history has too many examples when that trust has been breached. Our system of government is built on the premise that our liberty cannot depend on the good intentions of those in power; it depends on the law to constrain those in power.

Source: Anarchy and Christianity (1988), p. 23

Review of Aiken’s Life of Addison (1843)

Protectionism: the -ism which teaches that waste makes wealth, 1888, paragraph 155 http://oll.libertyfund.org/titles/sumner-protectionism-the-ism-which-teaches-that-waste-makes-wealth.

Source: Beyond the White House: Waging Peace, Fighting Disease, Building Hope