Quotations from Chapter 3 of Edward Gibbon's History of the Decline and Fall of the Roman Empire ("Of the Constitution of the Roman Empire, in the Age of the Antonines (96 - 180 A.D.)"):
The influence of the clergy, in an age of superstition, might be usefully employed to assert the rights of mankind; but so intimate is the connection between the throne and the altar, that the banner of the church has very seldom been seen on the side of the people. A martial nobility and stubborn commons, possessed of arms, tenacious of property, and collected into constitutional assemblies, form the only balance capable of preserving a free constitution against enterprises of an aspiring prince.
The character of the tribunes was, in every respect, different from that of the consuls. The appearance of the former was modest and humble; but their persons were sacred and inviolable. Their force was suited rather for opposition than for action. They were instituted to defend the oppressed, to pardon offences, to arraign the enemies of the people, and, when they judged it necessary, to stop, by a single word, the whole machine of government.
To resume, in a few words, the system of the Imperial government, as it was instituted by Augustus, and maintained by those princes who understood their own interest and that of the people, it may be defined an absolute monarchy disguised by the forms of a commonwealth. The masters of the Roman world surrounded their throne with darkness, concealed their irresistible strength, and humbly professed themselves the accountable ministers of the senate, whose supreme decrees they dictated and obeyed.
Augustus was sensible that mankind is governed by names; nor was he deceived in his expectation, that the senate and people would submit to slavery, provided they were respectfully assured that they still enjoyed their ancient freedom.
The two Antonines (for it is of them that we are now speaking) governed the Roman world forty-two years, with the same invariable spirit of wisdom and virtue. ... Their united reigns are possibly the only period of history in which the happiness of a great people was the sole object of government.
Antoninus diffused order and tranquility over the greatest part of the earth. His reign is marked by the rare advantage of furnishing very few materials for history; which is, indeed, little more than the register of the crimes, follies, and misfortunes of mankind.
The virtue of Marcus Aurelius Antoninus was of a severer and more laborious kind. It was the well-earned harvest of many a learned conference, of many a patient lecture, and many a midnight lucubration. At the age of twelve years, he embraced the rigid system of the Stoics, which taught him to submit his body to his mind, his passions to his reason; to consider virtue as the only good, vice as the only evil, all things external as things indifferent.
If a man were called to fix the period in the history of the world, during which the condition of the human race was most happy and prosperous, he would, without hesitation, name that which elapsed from the death of Domitian to the accession of Commodus.
(see also Gibbon _-_Table_of_Contents, Gibbon_-_Thoughts_Upon_Reading, ... and http://www.his.com/~z/gibbon.html for a single-page presentation of Gibbon quotes)
(correlates: TheVeto, Gibbon - Table of Contents, HerodotusOnFreedom, ...)