I understand your questions to be angled at political revolutions.
John Locke
The once influential idea that John Locke (1632-1704) wrote his Second Treatise of Civil Government in order to underpin the overthrow of James II and to justify the installation of William III (and Mary) is no longer tenable. The text was largely written in the early 1680s and Locke merely added contemporary references when the text was published in 1689. He did not write to 'establish the throne of our great restorer, our present King William; to make good his title, in the consent of the people, which being the only one of all lawful governments, he has more fully and clearly, than any prince in Christendom; and to justify to the world the people of England, whose love of their just and natural rights, with their resolution to preserve them, saved the nation when it was on the very brink of slavery and ruin' (Preface). Such passages merely gave the text a contemporary twist to apply to a revolutionary situation he favoured. Since it did have at least this intention we can see Locke as a philosopher involving himself in revolutionary politics, if not, post-Laslett, in the way traditionally believed. (Peter Laslett, 'The English Revolution and Locke's 'Two Treatises of Government'', The Cambridge Historical Journal, Vol. 12, No. 1 (1956), pp. 40-55.) [Peter Laslett, 1915-2001, was an English scholar and specialist on Locke who demolished the traditional idea that the Second Treatise had been written specifically to justify the Glorious Revolution.]
Richard Price
Price (1723-91), a nonconformist minister, was certainly a moral philosopher. His Review of the Principal Questions in Morals (1758, 3rd ed. revised 1787) is familiar to any student of 18th-century British moral philosophy. While he did not physically participate in the American and the French Revolutions, he was actively and enthusiastically involved in both. His Observations on the Nature of Civil Liberty, the Principles of Government, and the Justice and Policy of the War with America (1776) lent powerful and influential support to the American cause.
Since the beginning of the controversy between England and the colonies
Price had been an interested spectator, and he had kept in close touch with a
number of Americans by means of letters. He also had personal contacts with
Americans who were in London during the years preceding the Revolution,
among them Franklin and Josiah Quincy, jr., who was in London during the
winter of 1774-1775. From the start of the quarrel Price's sympathies had
lain with the Americans, and finally, after the outbreak of hostilities, he be-
came an active friend of the American cause. He conveyed information to
some members of Parliament who favored America."4 He likewise passed
on secrets to America, and had a number (176) assigned to him for use in correspondence. This espionage work was probably of little significance. A far greater service could be contributed by Price's pen.
In February, 1776, there appeared in London a pamphlet by Richard Price
entitled Observations on the Nature of Civil Liberty, the Principles of Gov-
ernment, and the Justice and Policy of the Wiar with America. Few pamphlets
of the eighteenth century were so widely read, so lavishly praised, or so bit-
terly condemned. Within two months fourteen editions had appeared in
London and over 6o,ooo copies had been sold. Price sacrificed profits by con-
senting to allow cheaper issues of the later editions. The pamphlet was also
published in French in Rotterdam, in German in Braunschweig, and in
Dutch in Leyden. Other editions appeared in Dublin and Edinburgh. The
city of London presented Price with the freedom of the city, in a gold box
worth fifty pounds. In America the pamphlet was as big a sensation. Two
issues appeared in Philadelphia, and others were made in New York, Boston,
and Charleston. It is no exaggeration to say that as a result of the pamphlet
"Dr. Price's name was in everybody's mouth."" In 1777 Price published a
second work on American affairs, called Additional Observations on the
Nature and Value of Civil Liberty, and the War with America . . ., and in
the year after that he brought out the two pamphlets in a new edition en-
titled Two Tracts on Civil Liberty . . ., for which he wrote a general introduction. (Carl B. Cone, 'Richard Price and the Constitution of the United States', The American Historical Review, Vol. 53, No. 4 (Jul., 1948), pp. 726-747 : 729-30.)
▻ American Revolution
It appears hard to deny that Price's ideas and arguments contributed to the climate of opinion in America in which revolutionary separation from Great Britain was seen as not only practicable but morally right. He was a revolutionary with his pen as effectively as if he had been a revolutionary on the battlefield.
▻ French Revolution
It was on November 4th, 1789, that Price preached the sermon
which provoked the Reflections on the Revolution in France [Edmund Burke's polemic against the revolution : GT]. The
occasion was the Revolution Society's celebration of the anniversary
of 1688, and Price took the opportunity to interpret the opening
events of the French Revolution to an audience in which enthusiasm
for those developments ran high. In this sermon, published under
the title 'A Discourse on the Love of Our Country,' he defended the
revolutionaries on the ground that they were inspired by those
"just ideas of civil government" which he believed had become
substantially though imperfectly embodied in the British Constitution. The aspirations of 1789 were to be justified by what he thought
were the achievements of 1688. (D. O. Thomas, 'Richard Price and Edmund Burke: The Duty to Participate in Government', Philosophy, Vol. 34, No. 131 (Oct., 1959), pp. 308-322 : 308-9.)
Again, if Price did not actively engage in the events of the French Revolution, he came out in active support of the revolution and hence involved himself in it.
Georgi Plekhanov
Widely regarded as Russia's first Marxist philosopher, Plekhanov (1856-1918) engaged in extensive revolutionary activity against the Tsarist regime in the later part of the 19th century - personally dangerous activity. He was acting at a time when the conditions for political revolution were not fully ripe; and his later politics were checked by disagreement with, then open hostility to, Lenin. But there is every reason to count Plekhanov as a philosopher who was also a revolutionary. See further : Samuel H. Baron, 'Plekhanov and the Origins of Russian Marxism', The Russian Review, Vol. 13, No. 1 (Jan., 1954), pp. 38-51.
Note on Socrates
From what little we know of Socrates, filtered mainly through Plato and Xenophon, Socrates was not a political revolutionary; he did not aim to overthrow the government. He did refuse to obey an order of the Thirty Tyrants who once had seized control of Athens (Apology, 32c-d) but when at his trial he was found guilty of impiety (irreligion) and of corrupting the youth of Athens (presumably by encouraging them to think for themselves), he asked for no clemency from the court. In prison he declined an offer from a litle knot of friends to fix his release so as avoid to the death penalty; he refused their offer on the grounds that by living in the city he had tacitly agreed - contracted or put himself under an obligation - to abide by the laws of Athens and would be violating the contract if he thwarted the court's verdict (Crito, 49d - 52a). His thinking was politically revolutionary in another way, however. He believed, so far as we can make out, in a politics of knowledge. To conduct politics properly required knowledge just as any other activity did. He did not believe, if Plato and Xenophon are to be credited, that the Athenian citizenry had the requisite knowledge; their democracy was the politics of ignorance. This represented a revolution in Greek political thinking as far as concerned its commitment to democracy.
